How Farmers Can Protect Water Quality, Replenish Aquifers and Save the Soil - a subject of great importance to for meeting the needs of the poor smallholder producers and for this consultation process, as trailed below:
Scientists work with farmers to find ways to reduce surface runoff and soil erosion, thereby also reducing water pollution. Dr. Mae-Wan Ho
A team of scientists and local farmers used a computer simulation programme to help identify the best ways to reduce surface runoffs and soil erosion on farms
[1].
The study was done in collaboration with the local authorities in an area of south-western France that suffers badly from surface runoffs and soil erosion
after rainfall.
To support the work, they used a geographic information system (GIS) computer simulation model of water flow and soil erosion, STREAM, to assess the impacts of a spring stormy event under different management scenarios at two sites chosen by the farmers. The results were jointly analysed and evaluated by the farmers and scientists, and the farmers discussed the technical and economic feasibility of each management scenario.
The STREAM simulations showed that a 40 mm spring rainfall with current cropping patterns led to 3 116 m3 total water runoff and 335 tonnes of sediment at site A, and 3 249 m3 water runoff and 241 tonnes of sediment at site B. Growing grass strips at strategic places could reduce runoff by about 40 % and sediment by about 50 % at site A. At site B, grass strips could reduce runoff and sediment by more 50 %, but changing the cropping system could eliminate both runoff and sediment almost entirely.
Agriculture & water
Agriculture is a major user and polluter of water, and this needs urgent attention in view of the global depletion of fresh water resources (see [2, 3]
World Water Supply in Jeopardy, SiS 56; Using Water Sustainably, SiS 57).
The problem started from the 1960s when intensive agriculture was introduced in Europe to increase crops yields (see [1]). This required mechanisation and the application of fertilizers and pesticides, which soon favoured big farms at the expense of small farmers. And the now well-known nvironmental problems of runoff, soil erosion and pollution of water resources started to emerge.
Over the past 20 years, groundwater and surface water monitoring in Europe revealed significant nitrate and pesticide contamination, especially in France, where surface water samples often exceed the drinking water limit of 0.1 mg pesticides/L. For example, 96 % of surface water in the Department Tarn and Garonne in south-western France was contaminated by nitrates, phosphorus and pesticides, partly because of erosive runoff in cultivated fields.
In 2000, the European Community introduced the Water Framework Directive (WFD) to restore and preserve the quality of all water resources. It set targets of water quality to be achieved by 2015. The common agricultural policy (CAP) reform of 2003 introduced the ‘cross-compliance principle’ that linked the full payment of CAP aids to farms to compliance with agri-environmental standards
called “good agricultural and environment condition”, which include a part of the annual cropped area to have permanent plant cover to prevent soil erosion and buffer strips (no-cultivated or grass planted) along water courses to prevent surface water pollution.
According to French decree, the total surface area of permanent plant cover (PPC) in each farm must be at least 3 % of the annual cropped area. PPC or grass strips must be planted within fields, most importantly, those bordering rivers, and the strips must be between 5 and 10 m wide and must cover at least 500 m2. Designing these agri-environmental measures (AEM) is not a trivial matter, and will differ for farms at catchment level as opposed to river level. Therefore modelling could help find the best design. And working with farmers in real farms would also put the model to proper test.
Farmers chose the sites
The study was done in the French Department Tarn et Garonne in collaboration with Lomagne district agricultural committee. Soil erosion is prevalent in these catchments and sediment loads in streams and rivers impact negatively on water quality.
The region has a humid temperate climate, with annual rainfall between 700 and 760 mm, and average daily temperatures 10 to 35 ºC. Rainfall is low to moderate in winter, and the most intense rainfall events are in spring. The soils in the region are very susceptible to surface sealing. The water table is very deep (> 10 m). The risk of erosive events is very high in April-May, when intense rainfalls occur (20-40 mm in 2 to 3 hours) and many fields have just been sown.
Figure 1 Sites selected for study in southern France
In collaboration with the local farmers, two sites were selected (see Figure 1). The first is a 41 ha hillside farm with slopes ranging from 0 to 15 %, comprising five large fields cultivated by two farmers. In 2009, 36 ha were planted with spring crops (maize and sunflower) and 5 ha with winter wheat. Spring storm causes mud flows in the fields with spring crops that cover the downhill road nearly every year. The second site is a 107 ha catchment that supplies the Serre River and comprises 40 fields cultivated by 5 farmers. This site is characterized by a steep-sided upstream valley with strong slopes (> 15 %), followed by a relatively flat valley (slope between 0 and 5 %). In 2009, five main crops were cultivated: winter crops (wheat, barley and rape) on 43 % of the area, spring crops (maize, sunflower and sorghum) on 41 %. Grasslands account for 12 % of the area mainly in the upper basin, while forest and set- aside account for less than 4 % of the area.
Site A was chosen because erosive runoff is severe and occurs almost every year in spring. Site B was chosen because it is small and different crops are grown
there. Another important factor was that most of the farmers (5 of 6) in the two sites selected agreed to spend time with the scientists.
The hydrological model and geographic information simulation software
Read the rest of this report at:
http://www.i-sis.org.uk/How_Farmers_Can_Protect_Water_Quality.php
Mr. Subhash Mehta