A. Name of watershed
B. Location (County or counties and State. For small watersheds it may be desirable to give in addition the legal description)
C. Size: area in acres or hectares
area in square miles or square kilometres
A. Climate (can get climatic data from Weather Bureau)
1. Precipitation (in inches or mm)
a) Total annualb) Seasonal (several breakdowns possible here-indicate months)c) Form (snow, rain--give percents of each if available) d) Maximum precipitation intensities (if available)
2. Evaporation (annual and seasonal if available)
3. Wind a) Prevailing wind direction b) Wind hazard high, moderate, or low
4. Other pertinent climate data such as relative humidity, climatic type, etc.
B. Geology and physiography
1. Size and shape
a) Area in acres or hectares Area in square miles or square kilometresb) General shape of watershed
2. Elevation in feet or metres: specify locations
a) At high point on divideb) At mouth or gaging stationc) At headwaters of permanent streamd) Fall of stream in feet per mile or metre per kilometre
3. Slope and aspect
a) Slope - proportion of watershed in different slope classesb) General orientation or aspect of watershed
4. Drainage features
a) Drainage pattern (dendritic, radial, annular, etc.)
b) Drainage density1) Number of well-defined channels per square miles or kilometres of watershed2) Miles or kilometres of permanent stream per square mile or kilometre of watershed
c) Location and description of lakes, bogs and swamps, if present
5. Parent rock--igneous, metamorphic, sedimentary
a) Percent of each and specific kindb) Condition of parent rock: solid, fractured, faulted, extent of outcrops.
1. Proportion of watershed area in:
a) Residual soilsb) Glacial material (specific type)c) Alluviumd) Volcanic materials
2. Distribution and hydrologic characteristics of major soil groups in watershed:
a) Depths: shallow, medium or deepb) Infiltration capacities (if available) texture classes give an indicationc) Depth of confining layers, if presentd) Surface drainage conditionse) Erosiveness of soil
D. Land use and cover conditions
1. Distribution by use classes: forest, range, agriculture, urban, metropolitan, etc.
2. ownership pattern
a) Public, private, industrialb) Stability of ownership
3. Forest land conditions (include fire history and past use where applicable)
a) List major forest types, their use and condition1) Good--good stocking, light or no grazing, good litter cover, no evidence or erosion, etc.2) Medium--moderate stocking, no overgrazing or excessive compaction, thin but continuous litter cover, no marked evidence of erosion,3) Poor--inadequate stocking, soil compacted heavy to overgrazing, thin or partial litter cover, sheet erosion or gullies present
4. Range land--indicate condition based upon evidence of overgrazing, type and condition of cover, soil compaction, pedestaling, erosion pavement, gullies, etc.
5. Agricultural land
a) Major agricultural economy (i.e., dairying, truck farming, etc.)b) Improper locations (steep, thin soils, etc.)c) Improper practices (up and down hill crops, clean cultivation, overgrazing in both pastures and farm woodlots)d) Amount of cropland under irrigatione) Agricultural drainagef) Extent to which conservation practices are applied
a) Urban and/or metropolitan areas within watershedb) Roads1) Road network: sparse, dense, absent2) Road conditions: primary and secondary roads
7. Other uses
a) Intensity of recreational use
1) Resort use
2) Wildlife resource
3) Fish resource
A. Erosion conditions along stream
1. Do floods occur frequently, periodically, seldom?
2. Season of year when most floods occur
3. Cause: high intensity storms, spring break-up, etc.
4. Maximum stage or heights
5. How much flood damage has resulted?
C. Stream flow
a) Source of streamflow (lakes, bogs, springs, ground water flow, accumulated snow, etc.)
b) Annual yield (in c.f.s. or c.m.s. and as percent of precipitation)
c) Seasonal yield
d) Maximum and minimum yields
e) Flow regime--do streams rise rapidly after rain, get low, or disappear in dry periods?
a) Do streams generally flow clear, turbid, turbid only in floods or high water stages?
b) Is water of poor quality or polluted?
1) Natural pollution--organic, drainage from swamp and bog areas
5) Hardness, mineral content
A. Source(s) of present supply surface water ground water
E. Power generation F. Recreation and wildlife
G. Other (e.g., sewage treatment)
H. Are present supplies adequate?
I. Will present supplies meet projected needs?
B. Flooding (including siltation)
C. Water supply
D. Water quality
E. Effects of land use on the problem(s)
1. Accelerated surface runoff, erosion, flooding
2. Water pollution
3. Reduced recreational values
4. Reduced standard of living
5. Unstable community
Source: Colorado State University.
A Treatment-Oriented Scheme especially for Hilly Watersheds
1 Symbols for most intensive tillage or uses:
C1 : Cultivable land 1, up to 7° slope, requiring no, or few intensive conservation measures, e.g. contour cultivation, strip cropping, vegetative barriers, rock barriers and in larger farms, broadbase terraces.
C2 : Cultivable land 2, on slopes between 7° and 15°, with moderately deep soils needing more intensive conservation, e.g. bench terracing, hexagon, convertible terracing for the convenience of four-wheel tractor farming. The conservation treatments can be done by medium-sized machines such as Bulldozer D5 or D6.
C3 : Cultivable land 3, 15° to 20°, needing bench terracing, hexagons and convertible terracing on deep soil and hillside ditching, individual basin on less deep soils. Mechanization is limited to small tractor or walking tractor because of the steepness of the slope. Terracing can be done by a smaller tractor with 8 ft (2.5 m) wide blade.
C4 : Cultivable land 4, 20° to 25°, all the necessary treatments are likely to be done by manual labour. Cultivation is to be practised by walking tractor and hand labour.
P : Pasture, improved and managed. Where the slope is approaching 25°, and when the land is to wet, zero grazing should be practised. Rotational grazing is recommended for all kinds of slopes.
FT : For food trees or fruit trees. On slopes of 25° to 30°, orchard terracing is the main treatment supplemented with contour planting, diversion ditching and mulching. Because of steepness of the slopes, interspaces should be kept in permanent grass cover.
F : Forest land, slopes over 30°, or 25° to 30° where the soil is too shallow for any of the above-mentioned conservation structures.
1. Slopes and the number of slope classes can be modified to meet country's needs and some F lands between 25° to 30° can be used for agroforestry purpose.
2. Any land which is too wet, occasionally flooded or too stony, which prevents tillage and treatment should be classified as: (a) below 25°: pasture; (b) above 25°: forest.
3. Gully dissected lands which prevent normal tillage activities: forest (over 25°) or pasture below 25°,.
4. Mapping Symbols: It could be labelled as follows:
Most intensive use
soil - slope - depth
32 - 2 - D
means: Cultivable Land 2
Wirefence Clay Loam - 7° to 15° - 36 in(90 cm)
Or, it could be simple labelled as C2.
(a) Slope classification
Slopes are divided into six categories, each having its implications for conservation treatments and the kind of tools to be used:
< 7° Flat to gently sloping. Broadbase terraces or other simple conservation treatments can be used up to 7°. Full mechanization for cultivation is applicable in this category. This slope class may not be common in hilly watersheds.
7°-15° Moderately sloping. Medium-sized machines such as a Bulldozer D5 or D6 can be employed for bench terracing. Four wheel tractor mechanization for cultivation can be applied.
15°-20° Strongly sloping. Small-sized machines such as b4 can be employed for conservation treatments. Small tractors, or walking tractors can be used for cultivation.
20°-25° Very strongly sloping. Manual for building the structures Hand labour and walking tractor for cultivation.
25°-30° Steep. Only for permanent tree crops such as food trees, fruit trees, forest or agroforestry. Manual labour for treatments.
>30° Very steep. Needs forest cover.
(b) Soil depth
Soil depth is divided into four classes. Here the depth refers to the effective depth of the soil which machine or manual labour can cut for conservation treatments and which plant roots can penetrate.
< 8 in Very shallow. Only on nearly level land can cultivation be (20 cm) practised.
8-20 in Shallow. Only below 20° slopes can this be cultivated with (20-50 cm) conservation treatments.
20-36 in Moderately deep. On a 25° slope, for instance, it needs about (50-90 cm) 30 in (76 cm) of soil to make narrow terraces of 8 ft (2.5 m) wide.
> 36 in Deep. No further soil depth classification is needed because (90 cm) the riser or terrace is limited to 6 ft height which is 3 ft cut and 3 ft fill.
(c) Other limiting factors
Land which is too wet, has poor drainage, occasionally floods or is too stony; which permanently limits the tillage or treatment, should be classified for lower or less intensive uses. On slopes under 25° such land can be used as pasture, whereas on slopes over 25° forest cover is proper so far as erosion control is concerned. Gully-dissected land which prevents any tillage activity should be put under permanent cover.
(d) Capability classes
Land is classified into its most intensive tillage or use. T ere are four major classes - cultivable land, pasture, food trees and forest . Only cultivable land has four sub-classes, each having implications for needed conservation treatments and tools to be employed. Use according to or within the capability class is encouraged, whereas use beyond the capability class is discouraged.
(e) Soil conservation treatment
In addition to the most popular conservation treatments on gentle slopes (below 7°) such as broadbase terraces and strip cropping, etc., six major treatments for steeper slopes are taken into account for the basis of the new classification scheme. These six treatments, which have been established in the hill slopes of Taiwan as well as in the western part of Jamaica under the UNDP/FAO project JAM/67/505, are particularly suited for the humid tropics. Bench terraces, hillside ditches and individual basins can be used to treat slopes up to 25° if the soils are deep enough. Orchard terracing can be applied from 25° to 30° slope. Convertible terracing and hexagons for full mechanization are to be employed on slopes up to 20°. All of them are mainly reverse sloped terraces of varying widths. Later another type of terracing was added: Intermittent terraces (see FAO Conservation Guide 13/3).
Microcomputers are now inexpensive and affordable in many developing countries. They can handle large quantities of watershed data, and may conveniently store, edit, retrieve, combine, update, and analyse them when needed. Many commercial software packages are available for various applications. Watershed managers worldwide are increasingly using microcomputers as a new tool to assist them in watershed survey and planning.
In addition to establishing a watershed database, mapping can be carried out more easily and rapidly with proper computer hardware and software. It is especially convenient when several maps are overlaid and manipulated to generate new spatial information. From an established database, detailed descriptive information can be combined with or extracted from maps readily.
This chapter will give a brief introduction to the subject. It will not explain the technical details of how computers and software are used, which would need a separate manual. Instead, this chapter will provide the planners and watershed managers some general guidelines and current information on using microcomputers for survey and planning.
Basic hardware for data management
Depending on the volume of data to be managed and whether the microcomputer is solely used for this purpose, the following suggestion is for average conditions (i.e. a watershed around 50 000 ha populated with 5 000 to 10 000 farmers). If the areas are bigger and farmers are more, branch offices would normally be set at sub-watershed level and each of them could have a set of equipment. The actual needs for hardware and software of a project, however, should be determined in consultation with an experienced computer expert.
- A microcomputer, IBM PC/AT or compatible with 640 kilobytes (KB) of RAM core storage, two floppy disk drives, and a hard disk of 40 Megabytes (MB).
- A 13 inch colour or monochrome monitor with compatible video card.
- A near letter quality printer, 9 to 24 pin dot-matrix type.
* Brands mentioned in this chapter are for reference only and do not constitute FAO's endorsement.
The most favourable purchase price for this set is around US$ 2 500. However many products with similar specifications may be available and it would often be worthwhile considering several alternatives before buying. Furthermore it is to be expected that prices for computer hardware will go down rather than up in the next five years.
Basic software for data management
There are now many software packages which are suitable and new software packages are constantly being developed which may be even better and cheaper than the existing ones. The following software are among the basic and popular ones which have been widely used or tested:
- DOS : This is a Disk Operating System. Its main functions are for managing disks and disk files. DOS also gives the operator complete control over the computer. It links between the operator and the computer. MS-DOS, produced by Microsoft Corporation is a system applicable to 50 leading microcomputers.
- Word Processors: These are convenient for preparing, editing, and presenting reports, Many commercial word processing software packages are available such as Word Perfect, Word Star, Multimate, and Wordmarc, etc. A careful selection is required to fit the actual needs.
- Spreadsheets: A spreadsheet is a powerful data analysis tool. It carries mathematical, statistical, and economic analysis functions, as well as database management and basic graphics. Lotus 123 is a spreadsheet that is widely used for technical analysis and modelling. It has a worksheet consisting of 256 columns and 8192 rows. The cells can be easily rearranged and edited. Cells can be built with dynamic formulas that refer to the contents of other cells. The data can be managed as a database, and can be transformed, modified, summarized and graphed. The possible applications are almost endless. For watershed survey and planning, spreadsheet models can be used for recording, analysing, retrieving, editing and monitoring physical data such as hydrology, land use and land capability, and socio-economic data as well. It can also be used for economic assessment, water balance estimation, and calculation of soil conservation treatment specifications.
- Database Management: A database, different from a spreadsheet, is an organized record. A database file consists of records and each of them has a series of fields. A field is the area that contains a particular item of information. Database management systems (DBMS) are specialized tools for storing information in a systematic order that allow the user to retrieve, extract, sort and synthesize them in a large data sets. dBASE IV (a relational DBMS) and PFS (Professional File System: a flat file DBMS) are some of the software used extensively. The latter is a simple file management programme for project managers and professionals. dBASE IV can be used for individual conservation farm planning records and also for keeping farmer's progress of work, cost and government contributions, etc. in a multi-file operation setting.
Special software for watershed modelling and soil conservation
- Watershed models: Watershed modelling is a growing field and it basically uses computers. In the past, models were only applied on expensive mainframe computers which have limited use in developing countries. Only recently has their applications on microcomputers become a reality. This will undoubtedly open new opportunities in many developing countries to verify, modify and adopt existing models or create new ones for planning and assessment uses. Many models have been developed over the last decade. The following list contains some selected ones having microcomputer applications:
1) AGNPS-PC (Agricultural Nonpoint Source Pollution Model) is a watershed model for estimating erosion, sediment transport, and nutrient loading in surface water. Agricultural Research Service, USDA, Minnesota Pollution Control Agency and Soil Conservation Service.
2) ANSWERS (Areal Nonpoint Source Watershed Environment Response Simulation) is a model to provide estimates of runoff, erosion and sedimentation for small agricultural watersheds (10 000 ha). Department of Agriculture Engineering, Purdue University.
3) CREAMS (Chemical, Runoff and Erosion in Agricultural Management Systems) is a field data model for assessing the chemicals, runoff and soil loss from agricultural practices. USDA-ARS, Tifton, Georgia.
4) PRMS (Precipitation-runoff Modelling System) is similar to ANSWERS but tracks additionally snowmelt, soil moisture, evapotranspiration and percolation during inter-storm periods to perform long-term water balance calculations. US Geological Survey, Lakewood, Colorado.
5) SWRRB (Simulator for Water Resources in Rural Basins) is to predict management effect on water and sediment yields in ungauged rural basins. USDA-ARS, Temple, Texas.
- Erosion, conservation planning and evaluation: Software packages for predicting erosion are many; mostly using USLE (Universal Soil Loss Equation) as a base. Software for soil conservation planning And evaluation is still limited the following gives examples of some available software:
1) ICE (Interactive Conservation Evaluation) is a program that combines Universal Soil Loss Equation (USLE) calculations and basic economic analysis for evaluating cost effectiveness of alternative conservation measures. USDA-Soil Conservation Service, Fort Worth, Texas.
2) LANDCONS is an expert computer system for land capability classification and conservation farm planning for small farmers on steep watershed slopes. Computer Assisted Development Inc. (CADI) and Colorado State University, Fort Collins, Colorado.
3) SP (Simple Process) Model is a surface runoff and sediment yield model for single rain storms over a homogeneous surface. USDA-ARS, Fort Collins, Colorado.
4) USLE and MUSLE are famous models used for erosion prediction for long-term average soil losses. USDA-ARS or USDA-SCS.
The above-listed software packages are either public domain or can be acquired with reasonable prices other erosion and watershed models which may be useful include:
- Silsoe Model (an erosion model) National College of Agricultural Engineering, Silsoe, Bedford, Great Britain;
- SMAP (Soil Moisture Accounting Procedure Model: modified version) University of Sao Paulo Brazil;
- Stanford Model (a watershed hydrology model.) Stanford University, California;
- WASED (a small forest watershed model) Rocky Mountain Forest and Range Experiment Station, Flagstaff, Arizona.
3. For watershed mapping and related information systems
Geographic Information Systems (GIS)
A Geographic Information Systems (GIS) is a set of computer programs which input, store, analyse, and display spatial and non-spatial data (CSU 1989). A modern GIS may be viewed as an integrated system composed of five main compartments: data input, database, model base, decision support system, and information display (Loran _et _al. 1988). GIS differs from computer-aided mapping (CAM) because the former is analysis oriented while the later is display oriented. In simple term, GIS has the capability of mapping with a full range of information interaction.
The major advantages of using GIS for survey and planning can be summarized as follows:
- they allow for a variety of manipulation including map measurement, map overlay, transformation, graphic design, and database management;
- stored spatial and descriptive data can be retrieved quickly;
- rapid and repeated analytic testing of conceptual models about geography can be performed i.e. for land capability and land suitability systems;
- comparisons of spatial information over time can also be efficiency performed, i.e. monitoring land use changes;
- certain analysis which can not be performed cost effectively by manual methods can be done by GIS i.e. terrain models, aspects;
- a rapidly growing field as it will further integrate with other data analytical tools.
GIS inputs of spatial data can be a) maps, b) aerial photos, c) special digital data such as satellite imagery, and d) textual and numerical data. The basic system outputs are: a) maps, b) graphics, and c) text including statistical tables, computed data files, etc. The entire system and its process can be seen from a simple diagram as shown in Fig. 12.
Before acquisition or development of such a system, planners and watershed managers need to consider thoroughly the following conditions.
1) Selection of a proper system to meet the requirement.
2) Consideration of the cost of initial acquisition.
3) The use of the system, whether limited to the present planning and monitoring work, or to be used for other projects or additional work.
4) Cost and techniques of converting existing data into a digital file i.e. digitizing, scanning, data conversion.
5) Proper maintenance including computer upkeep, skilled technicians, and software maintenance. This may require a special administrative unit and a regular annual budget.
GIS hardware and, software
Actual hardware and software needs for a project depend on objectives and availability of funds. Generally, in addition to a host computer, spatial data entry and display require the following basic hardware:
- a digitizer for map input;
- a digital tape drive if satellite image processing is involved;
- a colour ink plotter for map production;
- a mouse for screen manipulation and editing.
For the host computer, current estimates suggest that a 80386 microcomputer with 1.2 megabyte (MB) of internal memory supported by disk storage of some 100 MB or more are sufficient for many purposes. If it is insufficient for handling large data sets or for analysis-intensive projects, a 32 bit minicomputer should be acquired. Or, purchase a workstation with several microcomputers to share the work.
Hardware cost varies greatly depending on the type, source, sophistication, and the supporting equipment chosen (i.e. large plotters and digitizers are much more expensive than small ones). A moderate set of hardware including a host microcomputer, a colour monitor, a digitizer, a tape drive and a plotter cost around US$ 25 000 at 1589 price. A similarly configured minicomputer-based hardware will cost an additional US$ 25 000 to 40 000. A workstation will cost about US$ 4 000. GIS software may range from several hundred to ten thousand US Dollars and more. For example, the popular Earth Resources Data Analysis Systems (ERDAS) combining image processing capability and raster GIS, cost about US$ 25 000 for the basic hardware and software. With expanded hardware and software, the prices can easily reach US$ 50 000. Its GIS software module and Image Processing software module alone costs US$ 4 000 each. The popular PC Arc/Info system is a vector type GIS with topological structure and a relational database. The complete PC software package sells for about US$ 13 000. These prices, however, are still. affordable in many developing countries.
There are also some inexpensive GIS software packages. For instance, pMap (Raster system) costs about US$ 900, MapInfo (Vector system) costs US$ 750, and WOW (Both raster and vector), US$ 500 (all 1989 prices). These are systems all used on microcomputers. However, they have their usage under a specific set of conditions or have their special functions. The users should understand their advantages and disadvantages before acquiring them.
Recently, the International Institute for Aerospace Survey and Earth Sciences (ITC) of the Netherlands has designed a special GIS system called Integrated Land and Watershed Management Information System (ILWIS) which integrates many computer-based models (erosion, socio-economic. etc.) with map analysis and remote sensing systems.
4. A future outlook
Using microcomputers together with GIS, watershed models, and database programs for watershed survey and planning is a new trend. Microcomputer hardware and software will both be cheaper in the foreseeable future. Training opportunities for these subjects are increasing rapidly through regular school curricula or short courses. Because there are many advantages of using microcomputers and their costs are reasonable, some developing countries are starting to use them for watershed survey and monitoring work with good results.