MANAGEMENT OF WATER RESOURCES TOWARDS A NATIONAL DRAINAGE ACCORD - Muhammad Ramzan Chaudhry

Dr Muhammad Ramzan Chaudhry
Director, International Waterlogging and Salinity Research Institute
Lahore, Pakistan

SUMMARY

Agriculture plays a pivotal role in the economy of Pakistan. The country has an arid and semi-arid climate and is largely dependent on irrigation through a well established irrigation network. In spite of productive soils, suitable climate, irrigation and hardworking farming communities, yields are far lower than those of developed countries. This may be the result of inappropriate agricultural practices, inadequate or inappropriate use of fertilizers, inadequate pest control, insufficient and untimely irrigation water supplies and problems of waterlogging and salinity.

Drainage water has to be disposed off safely to suitable places without creating pollution. Because suitable sites are not always available, the only alternative is long-distance disposal at sea, without causing problems to people downstream.

Large numbers of public and private tubewells have been installed, but brackish water pumped by some of the tubewells needs proper disposal. Pipe drainage has been installed, from which effluent flows into water bodies. Industrial and urban effluents flow into the surface-drainage system and ultimately reach water bodies, polluting them badly. Agrochemicals have polluted groundwater, especially shallower aquifers. Heavy metals in industrial effluent, agrochemical pollution and untreated urban effluent are creating serious health problems. The quality of drainage water in most cases makes it unfit for irrigation. There is an urgent need for these effluents to be disposed of without adverse environmental effects.

Top priority must be given to formulation of an NDA, which must be acceptable to all provinces to avoid controversy. To reach such an agreed NDA, the following information will be needed:

• drainage-water quantity;

• drainage-water quality;

• groundwater quality and quantity;

• quantity and quality of receiving surface water;

• amount of water that can be reused after treatment for irrigation purposes;

• type and extent of pollution from drainage affecting water bodies;

• acceptable limits of pollutants;

• plans for drainage redesign where needed;

• water-quality standards and guidelines;

• strategy for provincial and inter-provincial institutions.

Roundtable meetings, seminars and symposia should be arranged to reach consensus on the NDA. Provided it is based on federal, provincial and community consensus, there is every possibility of its success.

INTRODUCTION

Pakistan's economy is largely dependent on irrigation because of its arid and semi-arid climate. The irrigation system, one of the largest in the world, consists of three major reservoirs, 23 barrages, 45 main canals and more than one million watercourses over about 16.47 million ha. The available water does not meet irrigation requirements; to augment inadequate supplies of good-quality water, poor-quality ground/drainage water is used.

In the late 1950s, inappropriate agricultural practices and inadequate drainage led to problems of sustainability: irrigated agriculture was confronted with increasing waterlogging and salinity. To address these problems, the Government of Pakistan through WAPDA constructed SCARPs by installing more than 16 000 high-capacity tubewells in fresh and saline zones, and over 500 000 private tubewells have been installed by the farming community. Fresh water from the tubewells is used conjunctively for irrigation, but brackish water is disposed of through drains into rivers, canals, evaporation ponds and the sea.

Chronic shortage of O&M funds for completed projects has limited success in controlling problems of waterlogging and salinity. To overcome this, the NDP was launched in January 1998 for a period of 25 years, at a cost of PRs31.4 billion (US$785 million).

A huge volume of drainage effluent from SCARPs is being produced, which is disposed of into water bodies. In rural areas, the drainage system is being misused by industrialists and municipalities passing effluents and sewage into it and polluting the drainage water. These pollutants are creating serious health hazards, because the water is used for human and animal consumption and to augment inadequate supplies of good-quality canal water. Unscientific use of this water is creating problems of salinity and sodicity, which are the main causes of soil degradation and abandonment. With increasing competition for water among agricultural, urban, industrial and recreational sectors, it is clear that this valuable resource must be managed more efficiently.

Objectives

The broad objective of the paper is to evaluate the quality and quantity of drainage water and its use for sustainable agriculture. Specific objectives are:

• assessment of drainage water quantity and quality;

• quality criteria and strategies for reusing drain water;

• protection of drainage-water from domestic and industrial pollution;

• policies and strategies for drainage-water allocation, use and disposal.

REVIEW OF LITERATURE

Agriculturists in arid and semi-arid regions are forced to use underground water, which is mostly brackish and cannot be used without treatment or appropriate technologies. Continuous use of such poor-quality water can result in soil deterioration and reduced crop yield. Research in Pakistan and abroad to study the effect of brackish groundwaters on soil and plants is reviewed below.

Groundwater quality in the Indus basin

The quality of underground water in arid and semi-arid regions of Pakistan is seldom comparable to canal supplies. Solute concentrations in river waters vary between 105 to 345 mg L^-1, whereas the sodium adsorption ratio (SAR) ranges from 0 to 4.37 (mmol L^-1)^½ and residual sodium carbonate (RSC) from 0 to 1.2 mmol L^-1 (Ibrahim and Hussain, 1988). Groundwater quality is generally not good, however, (Ahmed and Chaudhry, 1987) and becomes worse with increasing soil depth (Gupta et al., 1994).

Use of brackish water for irrigation can increase the resource base for irrigated agriculture, which will help to meet increasing national food requirements. During the last decade, the cropped area increased by 1.3 percent annually, whereas population increased by 3.1 percent annually; the gap between demand and production is widening with the passage of time (Malik, 1990). Pakistan has the largest contiguous gravity-flow irrigation system, capable of handling 130 billion m³ of water (Mohtadullah et al., 1993). Currently, water supplies are annually about 30 percent short even for the present cropping intensity (Badruddin, 1983).

Criteria for water suitability

The composition and concentration of the soluble salts present in all natural water determines its suitability for irrigation. Quality is normally evaluated according to three criteria:

• salinity: the effect of dissolved salts on crop growth associated with osmotic effects, expressed as EC;

• sodicity: the degenerative effect of excess sodium on soil structure, expressed as SAR;

• toxicity: the effects of particular solutes that damage plant tissue or cause an imbalance in plant nutrition, expressed in terms of ion concentration.

During early stages of SCARP planning, the only parameter considered was total salinity, i.e. the total dissolved-salt content of water (Zaidi et al., 1966; Hameed et al., 1966). Water with EC_iw up to 1.5 dS m^-1 was considered marginal and that with EC_iw above 3.0 dS m^-1 was deemed unsafe for irrigation in West Pakistan. Fireman and Haq (1966) calculated that if appropriate land and water management was effected, ECe would not increase for six years with the use of tubewell water with EC_iw 2.6 dS m^-1.

The SAR and RSC parameters were included later, along with total salinity, for defining irrigation-water quality for the SCARP development programme. At the WAPDA Mona Reclamation Experimental Project (MREP), Qayyum and Sabir (1975) conducted lysimeter studies for two and a half years with poor quality waters on medium textured soil to develop criteria for water suitability. In the light of results of studies carried out in SCARP, Younus (1977) reported that water with EC_iw up to 1.5 dS m^-1, SAR_iw <10 and RSC 2.5 mmol L^-1 was usable for irrigation purposes. EC_iw up to 1 500 meq L^-1, SAR_iw 10 and RSC 2.5 mmol L^-1 were safe and that RSC between 2.6-4.0 was not hazardous on medium-textured soils. In a field experiment on silty loam soil at MREP, Chaudhry et al. (1983) reported that water with total dissolved salts (TDS) up to 1 062 mg L^-1, SAR 9.12 and RSC up to 1.10 mmol L^-1 could be used without mixing with canal water to grow cotton. Muhammad and Ghafoor (1992) reported water-suitability criteria of various researchers. Water-suitability guidelines given by different researchers are given in Tables 1 and 2.

Table 1. Water-quality guidelines (Hussain, 1978)

a. For optimum management conditions.

b. For existing on-farm management conditions.

Table 2. Water-quality guidelines (Sheikh, 1989)

Effects of brackish water on soils

When soil is irrigated with water with a high solute concentration, its chemical properties such as EC, SAR, pH, soluble ions and exchangeable cations undergo important changes. These changes depend primarily on water quality and management practices (Qureshi et al., 1977, Aslam et al., 1988; Hussain et al., 1991 and Ghafoor et al., 1997).

When brackish water is used for several years for raising crops, the chemical properties of soil can change. The concentration and composition of salts in water determine the speed and nature of changes in soil (Kelley et al., 1940); ECe has been shown to increase linearly with EC_iw and the number of irrigations (Bhatti, 1986, Singh et al., 1992; Van Hoorn et al., 1993, Ghafoor et al., 1997). According to one estimate, 8 percent to 90 percent of ECe variability of soil is accounted for by EC_iw applied to crops grown on medium-textured soil (Haider and Hussain, 1981). The remaining variability in ECe may result from soil texture, drainage conditions and initial salt levels. Bhatti (1986) observed a linear relationship between ECe to a depth of 150 cm during the first three years in a clay loam soil with EC_iw 3.6 dS m^-1, SAR_iw 15.8 and RSC 6.8 mmol L^-1. After that, the rate of salt accumulation declined and the curve indicating salinity flattened. The average ECe of soil down to 150 cm rose from 1.23 to > 4/0 dS^-1 during this period.

Yasin et al. (1988) observed that ECe in the top quarter of the rootzone was 1.9, 1.6 and 1.4 times higher than that of EC_iw of 2, 3 and 4 dS m^-1 respectively; ECe of the original soil was 2.6 dS m^-1. The ECe of the soil increased significantly with rootzone depth: the lowest quarter of the rootzone was 6.5, 4.6 and 3.7 times higher than the EC_iw of 2, 3 and 4 dS m^-1, indicating that ECe did not increase in direct proportion to EC_iw.

The degree of salt accumulation varied with the water-holding capacity of different soils, a function of soil texture that has considerable influence on the build up of salinity and its effect on seed germination. Hamdy et al. (1993) reported that seedlings were better developed in fine-textured clay soil than in sandy clay soil, even though salt accumulation was slightly higher. In fine- and coarse-textured soils, salinity and SAR have been observed to rise from high to hazardous and reduce soil productivity in as little as three-and-a-half years (Haider and Farooqi, 1975). Singh and Bhumbla (1968) used water from 73 wells with EC_iw between 0.3 and 6.6 dS m^-1 and RSC 0.06 to 13.3 mmol L^-1. They reported that ECe was about half the EC_iw in soils with less than 10 percent clay, three-fourths in soil with 10-20 percent clay and 1.5 times in soil with >20 percent clay. In a lysimeter study, Hussain et al., (1991) observed greater ECe increase in sandy clay loam (1.6 to 8.2 dS m^-1) than in sandy loam (1.4 to 7.4 dS m^-1,with EC_iw 2.3 to 9.4 dS m^-1). This difference was attributed to the leaching behaviour of soils: there was more leaching of salts in sandy loam than in sandy clay loam. Chaudhry et al., (1983) concluded that salinity build up was greater in fine-textured clay loam than in coarse-textured sandy loam with water of TDS 2039 mgL^-1.

Rates of salinization and final salinity levels increase with irrigation; winter crops may vary according to the salt load of irrigation water, leaching and water-extraction patterns (Chaudhry et al., 1986, Pasternak et al., 1993, Bhatti, 1986). Higher ECe values appear at the upper level of the wheat-crop profile but at a lower level in the case of cotton (Naresh et al., 1993). Chaudhry, while working on water salinity levels of TDS 736, 1 056, 1 408 and 2 039 ppm, pointed out that ECe remained at safe limits of <4 dS m^-1 during maize growing with water salinity up to 2 039 meq L^-1, provided that SAR and RSC of the irrigation water were less than 5 mmol L^-1 and 2 mmol L^-1 respectively. Rainfall during 1976-79 was 2.29 cm, 11.03 cm and 12.4 cm for the three wheat crops, and 26.81 cm, 49.43 cm and 37.08 cm for the three maize seasons. Ghafoor et al. (1997) concluded that ECe was greater at the surface of moderately calcareous sandy-clay loam after wheat than after rice.

Poor-quality irrigation water increased concentrations of soluble salts in soils, precipitation of CaCO₃ and adsorbed Na⁺. Formation of NaCO₃ exceeded Ca²⁺ plus Mg²⁺. The use of such water would lead to sodic soil conditions (Kelley et al., 1961; Kelley, 1962). Significant correlations between exchangeable sodium in soils and RSC and SAR of irrigation water were reported by Hausenbuller et al. (1960). SAR_iw correlated positively with soil exchangeable sodium percentage (ESP) (Bajwa and Josan, 1989a). Eaton (1950) pioneered the concept of RSC and its consequences in the form of CaCO₃ precipitation and formation of NaCO₃.

Under normal management, SAR/ESP increased significantly in direct proportion to SAR_iw (Qayyum and Niazi, 1975; De Mooy et al., 1975; Khandelwal and Pal, 1991) and was more harmful for soils and crops than water with higher salinity (Haider and Farooqi, 1973). A proportional increase in soil SAR can be expected when SAR_iw increases (Haider and Hussain, 1976). Bajwa and Josan (1989b) investigated the possibility of predicting the sustained effect of irrigation water of varying sodicity on soil sodium saturation and crop yields in rice/wheat and millet/wheat systems. The irrigation water had EC 0.9, 1.6, 1.6, 1.45, 1.4 and 1.45 dS m^-1, SAR 0.4, 11.4, 12.1, 14.3, 15.8 and 19.5 and RSC 0, 2.4, 5.1, 7.6, 10.0 and 14.8 mmol L^-1. Continuous use of sodic waters increased the sodium saturation of soil.

Bajwa and Josan (1989a) note that in general a given EC_iw, higher SAR_iw results in increased sodium saturation in the soil, and reported that water with EC_iw 0.8 dS m^-1, RSC 10.3 mmol L^-1 and SAR 13.5 will create more sodium-saturated soil than water with EC_iw 0.8 dS m^-1, RSC 8.8 mmol L^-1 and SAR 8.4. Maximum sodium saturation in both cases occurred in the top 30 cm of soil and declined sharply with increasing depth. In the 60-150 cm soil layer, SARe and ESP values were low, only three to four units higher than those observed under canal-water treatment (EC_iw 0.24 dS m^-1, RSC 0 mmol L^-1 and SAR 0.4), which indicated that appreciable amounts of sodium had not moved to deeper layers in six years of irrigation with sodic waters. Build up of ESP in the upper layer of soil was higher than expected with water of SAR_iw 13.5 because of higher RSC and SAR at low electrolyte concentration. Precipitation of CO₃ therefore resulted in higher sodium saturation of soil. Singh et al. (1992) observed that at similar SAR_iw, irrigation with more saline waters (EC_iw 12 dS m^-1) caused greater accumulation of salts and increased soil-solution SAR. Leaching of salts by monsoon rains simultaneously reduced SARe, but higher SARe persisted in soils irrigated with water of higher SAR_iw and EC_iw. At similar EC_iw, increases in sodicity were related to higher values of SAR_iw. Even in lower soil layers, salts accumulated more with SAR_iw 40 than with water of lower SAR_IW (<20) at similar EC_iw because of structural deterioration. Reduced intake of rain or irrigation water would result in comparatively shallow displacement of salts during monsoons.

Development of sodicity in soil profiles is inversely related to irrigation, leaching fractions and rainfall. Leaching can reduce the development of sodicity (Muhammad et al., 1975; Yasin, 1983; Yasin et al., 1990; Sadiq and Chaudhry, 1993). In India, Gupta (1980) suggested that in high rainfall conditions of 650-750 mm per annum and adequate drainage conditions, water with RSC as high as 10 mmol L^-1 and adjusted SAR up to 20 can be used successfully on sandy loam soil.

When poor-quality irrigation water is used for a number of years, physical properties such as saturated hydraulic conductivity (Siyaz et al., 1983), bulk density and porosity (Costa et al., 1991), soil strength (Ghafoor et al., 1997) and infiltration rates (Chaudhry et al.,1983, Baumhardt et al., 1992) may be adversely affected. The concentration and composition of salts in irrigation water determine the speed and nature of changes induced in any soil (Abu-Sharar and Salameh, 1995).

Permeability problems can occur if irrigation water does not enter the soil rapidly. According to United States Salinity Laboratory staff (1954), if the hydraulic conductivity (HC) of surface soil is as low as 0.1 cm h^-1, leaching and irrigation may present serious difficulties. McNeal and Coleman (1966) presented detailed information about the effect of electrolyte concentration and ESP on the HC of seven soils. Quirk and Schofield (1955) showed that HC of soil decreased with increasing ESP, provided that electrolyte concentration was below a critical level. They combined the two parameters in their "threshold concentration" concept, which was defined as the salt concentration causing a 10 to 15 percent decrease in permeability at a given ESP. McNeal et al. (1968) suggested that a 25 percent decrease in HC was more appropriate. Shainberg and Letey (1984) tested the threshold concept: according to them, the choice of percentage of decrease in HC with ESP was arbitrary. Soils of HC up to 0.75 of the base value still have reasonably high permeability. They demonstrated that there was high variability in the HC of soils and that even the base HC could only be defined within ±10 percent. Soils in laboratory studies were usually more sensitive to sodicity and electrolyte concentration than soils in the field, so it is more appropriate to define a 50 percent decrease in soil permeability as critical and the combination of salt concentration and ESP required to produce a 50 percent change in permeability as the threshold. Threshold values of electrolytes may thus vary from soil to soil and cannot be forecasted without empirical tests, even for soils of similar clay content (Thomas and Yaron, 1968; Rhoades and Ingvalson, 1969). Oster (1994) presented detailed information about the effect of ESP and electrolyte concentration on the HC of soils in the western United States and Britain. HC of soils with ESP <10 was not affected by water with salinity >0.5 dS m^-1 (Fethendler et al., 1974; Pupisky and Shainberg, 1979; Shainberg et al., 1981). Infiltration rates decreased with increasing SAR_iw and EC_iw, suggesting that saline waters can be applied without detriment to physical soil properties, because high EC_iw offsets the effects of SAR_iw. This is not entirely true under field conditions. When saline water is applied, the ESP of surface soil balances the SAR_iw. As the soil water is concentrated by evaporation and evapotranspiration, ECe, SAR and ESP increase. Irrigation with nonsaline water or rainwater rapidly reduces ECe near the soil surface. Gupta (1990) demonstrated that both SAR_iw and RSC influence the physical properties of the soil. The permeability problem may become more serious during monsoons when irrigation is followed by the intake of rainwater (Schainberg et al., 1981; Minhas and Sharma, 1986). Oster and Schroer (1979) concluded that infiltration rates correlate better with irrigation water salinity and sodicity than with surface or column average exchangeable sodium and soil salinity. The mechanical action of applied water greatly enhances the effect of exchangeable sodium and soil-solution concentration on swelling and dispersion at the soil surface, which in turn affects infiltration rates. Yousaf et al. (1987) reported that increased clay dispersion and decreased HC were associated with decreased electrolyte concentration and increased SAR.

In the laboratory, reduced saturated (K), unsaturated HC and infiltration rates of soil columns are different from field conditions. Reduction in Ks was more pronounced with decreasing solute concentration and increasing SAR of the percolating solution (Dane and Klute, 1977). Minhas et al. (1994) observed that Ks and K(0) decreased at higher SAR_iw (20 and 40) and with lower EC_iw (6 dS m^-1). Zartman and Gichuru (1984) irrigated fine sandy loam soil with city water (EC_iw 1.5 dS m^-1, SAR 4.5) and blow-down water (BDW) (EC_iw 12 dS m^-1, SAR 11): greater decline in Ks (0.04 cm h^-1) was observed with high BDW relative to the control (0.74 cm h^-1).

Swelling results in aggregate breakdown or slaking (Abu-Sharar et al., 1987) and clay particle movement, which leads to blockage of conducting pores (Frenkel et al., 1978). The exact level of SAR_iw and EC_iw depends upon bulk density, clay content and mineralogy. Pupisky and Shainberg (1979) concluded that at low SAR levels and low salt concentration, dispersion and migration of clay into conducting pores was the major cause of reduced HC of surface soil. Swelling and dispersion increase with increasing SAR_iw or ESP and decreasing EC_iw, thereby influencing the physical properties of each soil in a unique manner (Oster, 1994).

Costa et al.(1991) studied the effect of brackish water on bulk density, saturation percentage and aggregate percentage of unsaturated soils used by Prunty et al. (1991). The cores of Parshal, Svea and William soil series with different EC, SAR, sand, silt and clay contents were irrigated with six samples of irrigation water of EC_iw 0, 1.20, 1.19, 1.25, 2.90 and 3.01 dS m^-1 and SAR_iw 0, 3.0, 3.1, 8.0, 9.2 and 19.5. In all soil series, at given levels of EC_iw, the saturation percentage increased by 0.2 percent for each unit increase in SAR_iw. Irrigation water with EC and SAR combinations of 1.2, 9.0, 3.01, 19.0 dS m^-1 and (mmol L^-1)^½ decreased by 79 percent and 69.2 percent, a greater aggregate percentage than water with high EC_iw and low SAR_iw. At depths of 0-15 cm, bulk density decreased 0.04 to 0.06 mg m-3 with water of EC_iw 2.98 dS m^-1 and SAR 8.0. This decrease in bulk density might be due to high Ca concentration in this water (6.3 to 11.9 mmol L^-1), which was 50 to 100 percent higher than the average of all other treatments. Zartman and Gichuru (1984) claimed that Na accumulation with EC_iw 12 dS m^-1 and SAR_iw 11.0 did not affect the bulk density of soil. Similarly, Ghafoor et al. (1997) observed no statistical difference in soil-bulk density with brackish water.

Plant response to brackish water

Continuous unscientific use of saline/sodic water has resulted in deterioration of soil health and reduced crop yields. Most agricultural crops irrigated with brackish water suffer and consequently glycophytes may decline or become uneconomical to grow (Minhas, 1996). Crop growth and yields are affected by irrigation with brackish water. Recent studies show that for saline agriculture, drainage water can be used successfully to grow crops without detrimental effect on plants or soils (Rhoades et al., 1989).

The literature indicates that it is not possible to define the limits of EC_iw, SAR_iw and RSC, because the effect of different qualities of water on soil health and crop yield is governed more by soil type, climate, and water management than the chemistry of irrigation water (Singh et al., 1992), particularly over short periods. Reduced yield is a common phenomenon resulting from poor-quality irrigation water; it varies under different soil types and agroclimatic conditions. In India, Yadav (1980) suggested that wheat can be grown successfully on sandy loam soil with water of EC_iw 8.0 dS m^-1. It was reported that the same crop can only be grown on the black clay soil with water of EC_iw 4.0 dS m^-1. In another field experiment at MREP, Chaudhry et al. (1983) observed that reduction in yield was greater in fine clay loam soils than that in coarse-textured sandy loam soils with the same EC_iw 3.2 dS m^-1 and climatic conditions. Water of EC_iw 3.2 dS m^-1 can be used successfully for economic crop production under comparable conditions, provided that SAR_iw is less than 5 and RSC less 2 mmol L^-1 on coarse rather than fine-textured soils.

Gupta and Yadav (1986) discussed critical limits of EC_iw for various crops in relation to soil texture. The critical tolerance limits of EC_iw decreases as soil texture becomes finer and rainfall decreases. The same crops are more tolerant to EC_iw in summer than winter, because of reduced rainfall. Wheat can be grown without any reduction in yield with EC_iw 5 dS m^-1 or with 10-25 percent reduction to EC_iw 10-12 dS m^-1 in coarse-textured soil. This critical limit of EC_iw for the same crop was narrow at 2.7 dS m^-1 for 10 percent reduction and 7.4 dS m^-1 for 25 percent reduction in wheat yields on fine-textured soil. Similar results regarding the critical limits of EC_iw for wheat were recorded by Dhir (1977), Haider and Hussain (1981) and Tripathi and Pal (1980). The relative grain yield (Y) for a given water salinity (X, EC_iw) can be calculated from the following relationship:

Y = 49.6889 - 0.0478x - 0.0978x²

According to this equation, EC_iw up to which percentage yield was less than 12.5, 12.5-25.0, 25.0-50 and >50 were respectively less than 8, 8-12, 12-16 and >16 dS m^-1. The corresponding ECe of soils at the wheat harvest was less than 6, 6-12, 12.2-20.4 and >20.4 dS m^-1. The quantity of rainfall during growth periods modifies the critical limits of EC_iw, SAR_iw and RSC. Kharif crops, which are grown during the rainy season, are less affected than rabi crops (Rehman and Hussain, 1981; Chaudhry et al., 1986; Chauhan et al., 1988; Singh et al., 1992).

Rice susceptibility depends on plant and environmental factors (Ponnamperuma, 1977). It can be grown with 10 and 25 percent reductions in paddy yield with saline water of EC_iw 1.8 and 4.0 dS m^-1 in summer and 2.6 and 4.4 dS m^-1 in winter. Girdhar (1988) reported that salinity delayed germination but did not affect final germination up to EC_iw 8 dS m^-1. Rice at EC_iw 8.3 dS m^-1 gave normal straw yields but significantly lower paddy yields compared to the control.

Girdhar (1988) reported that rice straw was more sensitive to RSC than grain yield. Ratios of straw to grain were 2.0, 1.9, 1.7, 1.6 and 1.7 for respective RSC levels of 0, 5, 10, 20 and 30 mmol L^-1. Water of SAR 16 adversely affected paddy yields (Jamil, 1972).

Reduction in dry-matter yield of sorghum has been reported by Muhammad (1967) Rehman and Hussain (1981), Bajwa et al. (1992) and Hassan et al. (1996) with higher levels of EC_iw, SAR_iw and RSC or their combinations. Muhammad (1967) reported that sorghum and maize dry-matter yields decreased linearly with an increase in EC_iw or SAR_iw. Rehman and Hussain (1981) reported that water of EC_iw of 3 dS m^-1 could be used on fine sandy loam soil without decreases in growth and yield of sorghum. Minhas et al. (1989) conducted a lysimeter experiment (2 × 2 × 3 m³) and reported that plant height, green- and dry-matter production and leaf area of sorghum decreased markedly with increasing EC_iw levels from 2.5 to 6.4 dS m^-1 on sandy loam soil. They pointed out that irrigation before sowing with good-quality water of EC_iw 0.32 dS m^-1 resulted in increased dry-matter yields of sorghum that were 18 percent better at EC_iw 4.7 and 52 percent better at EC_iw 6.8 dS m^-1 than when such water was used throughout the growing period. In a field experiment comparing different planting techniques for sorghum, they suggested that after irrigating sorghum planted in furrows with good-quality water, germination and dry-matter yields could improve with water of EC_iw 7.9 dS m^-1. Singh et al. (1992) used water in ten combinations of EC_iw (6 and 12 dS m^-1) and SAR_iw (5,10, 20, 30 and 40) for six years on sorghum in a wheat-sorghum crop rotation on sandy loam soil. To obtain critical limits of EC_iw and SAR_iw in relation to dry-matter yields of sorghum for 79 percent variability, they offer following regression equation:

RY(%) = 133.1 - EC_iw(5.58-0.0026R) - SAR_iw (0.0024R+0.43T) - 0.03(SAR_iw2 R2 = 0.79**),

where R = rainfall (mm), T = year and ** = significant at 0.05 probability.

On the basis of this regression equation, they suggested that the predicted value of SAR_iw for obtaining 75 percent potential yield of pearl millet/sorghum for an average rainfall of the area after five years come to 12 and 4 for EC_iw 6 and 12 dS m^-1, respectively.

THE PROBLEM OF WATERLOGGING

Waterlogging and salinity problems have resulted from arid climate, flat topography, seepage from unlined canals, poor water management, inadequate drainage, insufficient irrigation supplies and use of poor quality drainage water. Areas with watertable depths that vary in different periods are reported in Table 3. The data shows that from 1978 to 1998 areas with depth less than 1.5 m ranged from 9.0 percent to 18.3 percent, with similar variations observed in watertables from 1.5 m to 3.0 m and greater than 3.0 m.

Table 3. Watertable depths, April/June (Percent of CCA*)

*CCA: Cultural Command Area

STATUS OF DRAINAGE FACILITIES

Millions of hectares of agricultural land in Pakistan suffer from waterlogging and salinity, which severely restricts agriculture. Because the economy is 50 percent dependent on agriculture, waterlogging and salinity are not just agricultural problems, but affect the whole country. In the early 1960s, a massive effort to control waterlogging and salinity was undertaken. By June 1995, surface and subsurface drainage facilities had been completed in an area of 6.02 million ha at a cost of PRs25 billion. Projects costing PRs42 billion in an area of 2.96 million ha are under construction. An NDP is being implemented at a capital cost of PRs31.4 billion.

Drainage facilities installed up to June 1995 for controlling waterlogging and salinity are shown in Table 4. Surface drainage and subsurface tubewell and pipe systems cover an area of about 9 million ha.

Table 4. Status of drainage facilities in Pakistan (June 1995)

¹ FGW: FRESH GROUNDWATER;
² SGW: SALINE GROUNDWATER
Source: WAPDA, 1997

Maps of the drainage systems in four provinces are given in Figures 1 to 4.

Figure 1. Baluchistan surface drains

WATER RESOURCES AND REQUIREMENTS

Rainfall

Rainfall varies considerably, from less than 10 mm in some parts of the country to more than 500 mm in others, with most occurring during the monsoon from July to September; it contributes an estimated 7.4 billion m³ to crops in irrigated areas of the Indus basin.

Surface water

The Indus river system is the major water resource; the annual volume of river flow is about 199 million m³. Inflow to the rivers comes from snow, glacier melting and rainfall, and is highest during the monsoon. The present irrigation system comprises three storage reservoirs, 16 barrages, 12 main canals, link canals, branches and distributaries. Annual canal head withdrawals are about 128.5 billion m³.

Groundwater

Groundwater occurs mainly in the Indus plain, with some available in rainfed lands in the Barani area and mountain valleys. The Indus basin irrigation system covers about 16.47 million ha. Total groundwater withdrawal potential is given in Table 5.

Table 5. Groundwater potential and withdrawal in Pakistan (billion m³ [MAF])

Figure 2. Punjab major drains

Water requirements and availability in coming years are given in Table 6.

Table 6. Water requirements and availability, billion m³ (values in parenthesis are in MAF)

** Extrapolated

Figure 3. North West Frontier Province drains

Table 6 shows irrigation requirements of 177 billion m³ for 2000 and 255 billion m³ for 2013. Including non-irrigation uses, estimated water requirements would be 184 billion m³ for 2000 and 266 billion m³ for 2013. Water availability for these target years would be 134.2 billion m³ and 132.5 billion m³.

Reduction in the storage capacities of Tarbela, Mangla and Chashma reservoirs will lead to water shortfalls of 49.7 billion m³ for 2000 and 133.7 billion m³ for 2013. There seems to be little chance of enhancing water supplies in the near future by constructing water-storage structures on rivers.

GROUNDWATER DEVELOPMENT

During the late 1950s, waterlogging and salinity were considered to be the main obstacles to sustainability in irrigated agriculture. SCARPs, involving installation of large-capacity tubewells, were initiated, but for economic reasons priority was given to locating them in areas where the groundwater was suitable for supplemental irrigation, effectively making drainage a by-product (Afzal, 1997). More than 16 000 public tubewells (Table 7) have been installed in SCARPs.

Figure 4. Sindh major drains

Table 7. Progressive increase in tubewell installation

Source: Government of Pakistan (2000)

With the introduction of tubewell technology, development of groundwater through farmer-installed tubewells was started. Most of these tubewells were low-capacity. The progressive increase in tubewell installation is given in Table 7.

From Table 7 it is clear that from 1980-81 the number of public and private tubewells increased by 35 percent in 1986-87, 87 percent in 1992-93 and 166 percent in 1998-99. In 20 years, installation of public tubewells increased by 20 percent and private tubewells by 177 percent.

Figure 5. Percentage increase in tubewells over time

AREA IRRIGATED BY DIFFERENT SOURCES

Most of Pakistan is irrigated by surface water through a well established irrigation system. As surface water is not sufficient, groundwater is being exploited to augment it. The area irrigated by different sources is given in Table 8.

Table 8 indicates that 43 percent of the area is irrigated by pure canal water, and 57 percent by combinations of tubewells, wells and canals. Irrigation from sources other than canals helps to control waterlogging, but this groundwater may add salts to the soil, causing deterioration.

GROUNDWATER QUALITY

The quality of groundwater varies considerably in different parts of the country, both vertically and horizontally, ranging from fresh to extremely hazardous.

Table 8. Area irrigated by different sources (millions of ha)

*Nominal
Source: Government of Pakistan (2000)

Groundwater quality in the Indus basin

It is estimated that usable groundwater lies below about 60 percent of the Indus plain (Ahmed, 1993). Groundwater is generally fresh in strips along rivers because of seepage, deteriorating towards the centres of doabs. Groundwater salinity and quality distribution is given in Table 9 and Figure 6.

Table 9. Groundwater salinity distribution in the Indus plain (16.47 million ha)

Source: Ahmed, 1993

Figure 6. Groundwater quality of irrigated areas of Indus basin

Deep groundwater quality

Deep (120 m) groundwater quality is based on data from 876 test holes drilled during investigations of the lower Indus and 72 test holes drilled by WAPDA planning organizations and consultants. Table 10 gives the areas in various ranges of groundwater quality, and shows that of the Punjab command area of 9.84 million ha, groundwater salinity is less than 1 000 ppm in 55.7 percent, less than 1 000-1 500 ppm in 13.8 percent, less than 1 500-3 000 in 13.5 percent and less than 3 000 in 17.0 percent.

Table 10. Area with different water quality (TDS) to a depth of 120 m

Source: Zuberi (1999)

In NWFP, the areas in these categories are 82.4 percent, 5.2 percent, 12.4 percent and 0 percent; in Sindh and Baluchistan they are 9.8 percent, 5.3 percent, 8.8 percent and 76.1 percent. This indicates that deep groundwater quality is best in NWFP, followed by Punjab, Sindh and Baluchistan. Groundwater quality is marginal to hazardous in about 50 percent of the irrigated area. If this area is waterlogged, drainage and suitable locations for effluent disposal will be required.

Shallow groundwater quality

Table 11 shows that in Punjab, 65.4 percent of the total area of 9.84 million ha has shallow (40 m) groundwater salinity up to 1 000 ppm, 12.2 at 1 000-1 500 ppm, 9.8 percent at 1 500-3 000 and 12.6 percent at 3 000 ppm. In NWFP, of the total 0.4 million ha, the figures are 82.4 percent, 5.2 percent, 12.4 percent and zero. In Sindh and Baluchistan, of the total 6.25 million ha, the figures are 17.2 percent, 6.6 percent, 13.8 percent and 62.4 percent. Usable groundwater lies beneath over 57 percent of the area; brackish water lies beneath 42 percent. In cases of waterlogging, effluent needs to be disposed of in environmentally safe ways with agreement by all provinces.

Table 11. Area with different water quality (TDS) to a depth of 40 m

Source: Zuberi (1999)

CHANGE IN GROUNDWATER QUALITY WITH PUMPING AND TIME

Change in tubewell/ground-water quality in Punjab

Public tubewells are operated to augment inadequate supplies of good-quality canal water and to control the waterlogging and salinity problems. With constant pumping for a long time, the quality of tubewell water has deteriorated as the percentage of marginal to hazardous water has increased (see Table 12).

Table 12. Changes in tubewell/groundwater quality in Punjab

Source: SCARP Monitoring Organization (SMO) (1994)

Changes in tubewell/ground-water quality in Sindh

Table 13 shows that water quality has deteriorated except in Larkana Pilot Project, where some improvement was observed. Deterioration in groundwater quality will have negative impacts on drainwater quality.

Table 13. Changes in tubewell/groundwater quality in Sindh

Source: SMO (1994)

Change in tubewell/ground-water quality in NWFP

In contrast with the other provinces, NWFP tubewell water quality improved with pumping and time except in Banu SCARP, where slight deterioration was observed (see Table 14). Groundwater quality is better in NWFP than Punjab or Sindh.

Table 14. Changes in tubewell/groundwater quality in NWFP

Source: SMO (1984)

GROUNDWATER/DRAINAGE WATER CONTAMINATION

Groundwater, especially shallow, and drainage water may be contaminated from many sources, some of which are described below.

Agrochemicals

Fertilizers

During the last three decades, the use of fertilizers, especially nitrogen, has increased consi-derably (see Figure 7). Excessive irrigation or rainfall can leach down NO3-N, which is the main source of contamination. Increased use of N fertilizers may result in groundwater pollution, especially shallow groundwater present in about 17 percent of the irrigated area. If groundwater is contaminated, drainage water will inevitably be affected.

Figure 7. Use of N fertilizer in Pakistan

Pesticides

Pesticide use has increased greatly with the passage of time. About 75 percent of the insecticide is used on the cotton crop alone; the rest is used on rice, sugarcane, maize and vegetables (Hussain, 1996). Excessive use of pesticides has created environmental problems such as residues in food, soil and groundwater, pest resistance and health hazards. Mubarik and Jabbar (1992) found that seven out of ten water samples were contaminated with one or more pesticides (Table 15).

Table 15. Concentration of pesticides in groundwater from selected sites in Pakistan

Source: Mubarik and Jabbar (1992).

Parveen and Masud (1988) reported the presence of chlorinated pesticides or their metabolites in cattle drinking water; some samples were found to contain benzene hexachloride (BHC) between 1.0 and 16.4 mg L^-1. The presence of such chemicals can affect animal and human health and fish production.

Industrial effluents

There are now numerous large and small industries whose effluent is discharged untreated into surface drains and ultimately water bodies. This water is used downstream for irrigation and even human consumption. EPA studies show values for Cr of 2-20 mg L^-1 in electroplating effluent and 20-300 mg L^-1 in tannery effluent, compared with a national standard of 10 mg L^-1. Khan et al. (1992) reported that in di-ethylene triamene pentacetic acid (DTPA) extractable soil Cd, Fe, Cu and Mn were higher where city effluent had been used for 5-20 years than where soil had been irrigated with canal water (see Table 16). In soils irrigated with city effluent, Cd and Co were within safe limits; Mn was within permissible limits where city effluent was used for irrigation (Murtaza et al., 2000).

Table 16. Accumulation (ppm) of heavy metals in soil

Sadiq (1999), investigating the use of city effluent to irrigate vegetables, found that Cu, Fe, Pb and Zn decreased with increasing soil depth. Cu, Fe, Zn concentrations exceeded safe limits in the upper 20 cm of soil; Pb was within safe limits.

Bacterial groundwater pollution

Tahir et al. (1994) reported that 90 percent of drinking-water samples were polluted with coliform bacteria; almost all privately dug wells in the Rawalpindi area contain bacterial contamination.

Ziai (1993), in a study carried out on 160 ha near Faisalabad where waste water was used for irrigation, found that groundwater had high chloride and total dissolved solids throughout the study area, in concentrations ranging from 846 mg L^-1 to 2 768 mg L^-1. Fecal coliform density levels were high and did not meet World Health Organization (WHO) standards for unrestricted crop irrigation (Shuval et al.1986).

Irrigation water

Irrigation is constantly adding salts to the soil. If not properly managed, this can cause secondary salinization. Some of these salts find their way into groundwater from excessive irrigation or rainfall. Mellor et al. (1994) indicated that irrigation water with a salt content of 200 ppm adds 0.28 tonnes per ha per year, of which 75 percent goes into groundwater.

Aquatic pollution

Karachi's 2 605 industrial units, including major companies such as Sind Industrial Trading Estate (SITE), Land Industrial Trading Estate (LITE), Korangi and West Wharf, discharge all their effluents into the Malir and Lyari rivers. These flow into Korangi Creek, which consequently receives a heavy load of organic effluents and salts of heavy metals, which endanger coastal aquatic life.

Industrial-pollution surveys carried out by the Government of Pakistan in 1989 in industrial areas in Karachi, Multan, Faisalabad, Kalashah Kaku (Lahore), Noshera and Peshawar reveal that industries are discharging untreated effluents containing high concentrations of pollutants, including toxic-metal salts, bacteria, acids and oils, into water bodies, causing soil, ground and drainage-water contamination (see Tables 17 to 20).

Table 17 shows that all the industries discharge effluents with heavy metal concentrations and other pollutants. Although such disposal has led to extensive degradation of soils and water, only limited efforts have been made to impose regulatory measures. Unless such measures are developed, the current rate of environmental degradation will increase, jeopardizing valuable agricultural land, groundwater and drainage resources.

Table 17. Toxic substances (mgL^-1) in effluents of sample industries in Karachi

Source: Hussain et al. (1996)

Table 18. Pollution load in effluents of sample industries in Multan

* Biological oxygen demand
Source: Hussain et al. (1996)

Table 19. Pollution load in effluents of sample industries in Faisalabad

Source: Hussain et al. (1996)

Table 20. Pollution load in effluents of sample industries in Nowshera

Source: Government of Pakistan: Environmental Profile of Pakistan (1989).

Water bodies in urban and rural areas serve to dispose of irrigation and drainage water and domestic and industrial wastes. Most effluents come from urban centres, where much of the population resides. Urbanization is one of today's major environmental problems (UNESCO-UNEP, 1983): cities with populations greater than one million are estimated to accommodate 36 million people (Government of Pakistan, 1989).

Untreated domestic sewage

It is estimated that 2×10⁶ tonnes of wet human excreta is produced annually, of which 50 percent goes into water bodies. Water-pollution problems are assuming serious proportions, particularly around major urban centres. Environmental profiles of Pakistan indicate that about 40 percent of deaths are related to waterborne disease. Sewage with a high biological oxygen demand (BOD) exhausts aquatic O₂, which creates unpleasant taste, odour and anaerobic conditions in water bodies.

Major cities in Pakistan dispose of largely untreated sewage into irrigation systems without considering their capacity. This leads to serious bacterial contamination, which threatens human health. The organic load of sewage seriously depletes the dissolved oxygen content of the receiving water, causing anaerobic conditions and making water unfit for fish. Fish production in the river Ravi, which receives untreated effluent from Lahore, has been reduced by 5 000 tonnes per year (Saleemi, 1993).

Sewage generated in human settlements is sometimes disposed of directly into fields, mostly around large cities, where vegetables are generally grown. These fields act as reservoirs of disease agents such as mosquitoes, lice, ticks and other parasites.

Living organisms are perhaps the greatest impediment to safe water supply. Access to clean water is available to only 77 percent of the urban population in Pakistan. In Karachi, for example, 38 percent of the population have water connections in the home; the rest depend on community standpipes, water tankers and private water bores. Other areas may be less fortunate. In the 45 000 major towns and villages of Pakistan, water is often drawn from open, untreated sources. Rural water supplies are particularly exposed to infestation by rodents, insects, flatworms, roundworms and micro-organisms. Many waterborne diseases are spread through drinking water. Gastro-intestinal disorders and serious infectious diseases such as polio, salmonella, hepatitis, cholera, typhoid and tuberculosis are spread through polluted water. There is evidence that water contamination has begun to threaten the food chain. In Rawalpindi, Islamabad-area milk and milk products, fruit and vegetables have been found to be infected with salmonella, E. coli, coliforms, Bacillus cerus and other pathogenic bacteria. This is particularly prevalent when seasonal stream waters are used for irrigation. In view of the precarious soil environment, water pollution is a serious issue in Pakistan.

QUALITY OF DRAINAGE WATER

There is no regular system for monitoring the quality of drainage water. The available information on drainage-water quality in some areas is briefly presented below.

Water quality of surface drains in Rachna Doab

Samples were taken upstream and downstream of branch-drain junctions with main drains, subjected to complete chemical analysis and categorized as usable, marginal and hazardous on the basis of EC, RSC and SAR. Details are shown in Table 21.

Table 21 shows that during the 1991-92 monsoon, 266 water samples were collected from surface drains running in Rechna Doab, of which, 111 (41.7 percent) were usable, 46 (17.3 percent) marginal and 109 (41.0 percent) hazardous.

Table 21. Water-quality categories of Rechna Doab drains (1991-92)

Source: SMO publ. SM 236.

Surface drains running in upper Rechna Doab generally discharge good-quality water; the exception is Chichoki Mallian drain and its tributaries, which discharge hazardous water. It is clear that almost all the drains flowing from central to lower Rechna Doab discharge highly brackish water. A few sites on Jaranwala main drain, Marh Chiniot drain and certain small drains and nallahs running in upper Rechna Doab have produced marginal water.

Geochemical types of surface-drain water in Rechna Doab, December 1991-January 1992

Geochemical classification was made using Stiff's method, in which dominant cations and anions determine geochemical type. In Rechna Doab, 266 water samples were collected from different drainage systems. A summary of geochemical types is given in Table 22.

Six types of water were present in Rechna Doab drains: NaHCO₃, Ca(HCO₃)₂, NaCl, Na₂SO₄, CaCl₂, and Na CO₃. Of the 266 samples collected during 1991-92, 132 (49.6 percent) produced Na₂CO₃, 65 (24.4 percent) Ca (HCO₃)₂, 47 (17.7 percent) NaCl, 19 (7.1 percent) Na₂SO₄. 2 (0.8 percent) CaCl₂, and 1 (0.4 percent) Na₂CO₃. Sodium-bicarbonate water was dominant in Sheikhupura, Jaranwala, Marh Chiniot, Q.B. Link and Chichoki Mallian, while in Summandri drainage system, sodium-chloride water remained dominant. As in groundwater in Rechna Doab, bicarbonates of sodium, calcium and chlorides of sodium remained dominant in drains; calcium chloride and sodium carbonate water was insignificant.

Table 22. Summary of geochemical water quality of drains

Source: SMO Publ. SM 236

Range of water-quality parameters in Rachna Doab drainage water

The water is classified for irrigation purposes on the basis of EC, SAR and RSC. The range of different water quality parameters is presented in Table 23.

Table 23. Range of water-quality parameters in Rachna Doab drains, 1991

Source: Publication No. SM 236

Water quality of surface drains in Chaj Doab, 1990-91

Monitoring of surface drains in Chaj Doab was carried out in December 1990 and June 1991. Samples were taken upstream and downstream of branch-drain junctions with main drains, subjected to complete chemical analysis and categorized as usable, marginal and hazardous on the basis of EC, RSC and SAR. Details are given in Table 24.

Table 24 shows 157 (51.7 percent) water samples categorized as usable, 67 (22.0 percent) marginal and 80 (26.3 percent) hazardous. During the second cycle of 323 water samples, 145 (44.9 percent) were usable, 45 (13.9 percent) were marginal and 133 (41.2 percent) hazardous.

Table 24. Water-quality categories of Chaj Doab drains

* Panjan Raju Khori
Source: SMO publ. SM 211.

Surface drains in upper areas of the doab drain mostly usable water; those in the lower part drain saline water. Drains in the extreme southwest remain mainly dry; their function is to drain water from heavy rains and floods.

Changes in water quality of Chaj Doab surface drains between December 1990 (after monsoon) and June 1991 (before monsoon)

For assessment of chemical changes in water quality of surface drains, samples were categorized into usable, marginal and hazardous. Details are given in Table 25.

Geochemical aspects of surface-drain water in Chaj Doab

Geochemical classification using Stiff's method was carried out; five types of water - NaHCO₃, Ca (HCO₃)₂, Mg(HCO₃)₂, NaCI and Na₂SO₄ - were identified and are given in Table 26.

Table 25. Water-quality categories of Chaj Doab drainage water

Source: SMO publ. SM 211.

Table 26. Summary of geochemical water quality of Chaj Doab drainage water

Source: SMO publ. SM 211.

Bicarbonates of sodium and calcium are predominant in water from PRK, Upper Budhi nallah, Lower Budhi nallah and small drains nearby; sodium chlorides are predominant in water from FS, Mona, Rani Wah and small drains in the vicinity.

Table 27. Range of water-quality parameters in Chaj drainage water, 1990

Source: SMO publ. SM 211.

Range of water-quality parameters in Chaj drainage water

The EC (salinity), SAR and RSC of Chaj drainage water are shown in Table 27.

Ground and surface water quality of SCARP VI saline zone (1989-1992)

In the first stage, only 391 of 514 drainage tubewells were installed along four drains: Abe-Hayat, Khanpur main, Manthar and Pattan Manara. Tubewells were sampled under a regular monitoring programme: 326 in 1989-90 and 331 in 1990-91. In the second stage, the remaining 123 tubewells were installed along Tarukari drain and sampled during 1991-92. Water quality and percentage increase of tubewells during both periods are shown in Table 28.

Table 28 shows that water from tubewells along Abe Hayat, Manthar and Pattan Manara remained 100 percent hazardous in both periods; along Khanpur Drain it was 1 percent usable, 4.1 percent marginal and 94.9 percent hazardous during 1989-90. All 75 tubewells sampled during 1990-91 were classified as hazardous.

Table 28. Water quality and percentage change with time

Source: SMO publ. SM 235.

Water-quality monitoring of 123 tubewells along Tarukari Drain was conducted during 1991-92, but only 61 could be sampled. Details are given in Table 29.

Table 29. Water quality of Tarukari drainage tubewells, 1991-92

Source: SMO publ. SM 235.

Table 29 shows that water from 16 (26.2 percent) tubewells was usable, 23 (37.7 percent) was marginal and 22 (36.1 percent) was hazardous. Seepage of canal water from the adjacent Punjnad main canal and Abbasia canal is the main source of recharge, which is why tubewells along Tarukari drain and its branches pumped out usable (26.2 percent) and marginal (37.7 percent) water.

Drain and pond water quality

Five hundred and fourteen drainage tubewells of SCARP-VI saline zone discharge into Abe Hayat, Khanpur, Manthar, Pattan Manara and Tarukari drains, either directly or through branch drains. The effluent from all these drains is ultimately disposed of into ponds. Table 30 shows samples and water quality.

Table 30 shows that all effluent from all the drains is hazardous. If the system is not drained out properly, soils in adjacent areas, socio-economic conditions and the local environment will be adversely affected. To avoid these problems, measures should be taken immediately by agencies and departments concerned.

Table 30. Drainage-water quality, SCARP VI

Source: SMO publ. SM 235

Range of water-quality parameters in SCARP VI

The range of water-quality parameters such as EC, SAR and RSC of SCARP VI water is presented in Table 31. It is clear that the water is totally hazardous and cannot be used for irrigation purposes. The only alternative for such water is safe disposal to sea or elsewhere through adequate drainage systems, which must not create environmental problems in adjoining areas.

Table 31. Range of water-quality parameters in SCARP VI, 1990-91

Source: SMO publ. SM 232.

WATER QUALITY OF LBOD

Quality monitoring of the LBOD system was carried out by the WAPDA SCARP Monitoring Organization. Results are given in Table 32.

Table 32. Water quality of LBOD

Source: ISRIP publ. 1996.

It is clear that water from almost all the drains is of poor quality and cannot be used for irrigation. If approprriate technologies are adopted, it may be possible to render this water usable.

TOWARDS AN NDA

IWASRI has already started work on re-use and safe disposal of drainage water under the NDP. Other institutions have research in progress on use of brackish water for crop production, the outcomes of which will provide technical feed back for formulation of the NDA. An integrated, comprehensive approach may be needed to resolve problems and fulfil stakeholders' requirements.

Issues

The main issues requiring attention for the sustainability of irrigated agriculture in Pakistan are listed below.

• One of the largest gravity-flow irrigation systems is without adequate drainage facilities.

• Salt balance is a prerequisite for the sustainability of irrigated agriculture. Salt brought by irrigation water and mobilized through drainage needs to be disposed of in suitable manner outside the system to avoid salt buildup.

• Increasing problems of waterlogging and salinity led to implementation of large drainage projects.

• Large volumes of drainage effluent need environmentally safe disposal or reuse.

• O&M of drains is inadequate.

• Drainage-water quality is poor.

• Drainage water is often contaminated.

Information required

The following basic information will be needed to plan the NDA;

• volume of drainage water produced and to be disposed of;

• quality of drainage effluent;

• areas affected;

• pollutants being added;

• facilities available for disposal;

• possibilities for reuse and farmers' responses;

• protection of drainage-water quality.

For the above information, the following are needed:

• a comprehensive network for monitoring quantity and quality;

• development and dissemination to farmers of technology for reuse of drainage water;

• protection of drainage-water quality from untreated industrial or urban sewage.

Organizations

The following organizations are envisaged:

• federal level (NDP), dealing with drainage system at national level;

• provincial level (PIDAs), dealing with drainage systems at provincial level, with active farmers' participation;

• farm level, dealing with on-farm drainage systems with farmers' participation;

• WAPDA: comprehensive and continuous monitoring at national level with coordination of the Environmental Protection Agency (EPA) and environmental protection departments (EPDs);

• research: coordinated national and provincial departments.

Implementation

Preparation of an NDA has been decided by the Executive Committee of the National Economic Council (ECNEC). The proposal should set out the responsibilities of national and provincial organizations for an efficient and environmentally sustainable national drainage system.

The national drainage system part of the NDP is envisaged as an interconnected system of federally owned and operated outfall drains for the entire Indus basin to carry saline drainage effluent to the sea. It will act as a control to the long-term drainage strategy and River Basin Management (RBM) programme for the Indus basin.

The National Surface Drainage System (NSDS) will require development of a large framework for cost sharing, operation, financial planning, environmental and resettlement issues agreed by four provinces, federations and WAPDA.

It is strongly recommended that to avoid future controversy, an inter-provincial drainage accord parallel to the Inter-Provincial Water Accord should be evolved and implemented well ahead of the commissioning of NSDS.

CONCLUSIONS AND RECOMMENDATIONS

Conclusions

1. Drainage-water quality varies considerably.

2. More than 15 percent of the area is waterlogged.

3. Groundwater is fresh in strips along rivers and deteriorates in the centre of doabs.

4. 16 000 public and over 500 000 private tubewells have been installed.

5. Tubewell installation increased by 166 percent in two decades.

6. Less than 50 percent of the area has groundwater salinity less than 1 500 ppm.

7. Groundwater quality deteriorates over time with pumping.

8. Shallow (40 m) groundwater quality is better (57.4 percent) than deep (120 m) groundwater (49.3 percent).

9. Groundwater contamination with N-NO3 has resulted from increased use of N fertilizers.

10. Pesticides have contaminated groundwater in some cotton-growing areas.

11. Untreated industrial effluent has contaminated groundwater.

12. Irrigation water with 200 ppm salinity adds 0.28 tonnes of salts per ha per year, of which 75 percent go into the ground.

13. Large volumes of drainage water need environmentally safe disposal.

Recommendations

1. Waterlogging and salinity must be managed properly.

2. Shallow groundwater quality should be assessed regularly.

3. Agrochemicals should be applied with great care; polluted groundwater cannot be reclaimed.

4. Industrial effluent and city sewage must be treated before disposal.

5. A national drainage system should be developed as part of the NDP.

6. A framework should be developed for financial and environmental management, agreed by the provinces, federations and WAPDA.

7. An inter-provincial drainage accord should be evolved and enforced.

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