Spatial Decision Support System for Watershed Prioritization and Evaluation of Conservation Strategies
Watershed Based Management for Sustainable Development Decision Support Technique; Land Potential Evaluation
Nagwan watershed, Hazaribagh district, Jharkhand (INDIA)
23°59'-24°05'N and 85°18'-85°23'E
Estimating (Predicting) sediment yield from a test-watershed, in Damodar-Barakar catchment, under current resource management systems and identifying those specific areas within the watershed which have high potential for soil loss (i.e. Watershed Prioritization) thereby;
Saving on cost and time involved in such large scale monitoring of erosion processes in individual fields within a watershed
Focusing most of the available central / state government funds in only high priority areas.
Evaluating alternate resource management strategies in the test watershed (i.e. Impact Assessment).
In reality, it is not possible to collect silt data actually from all watersheds in a country and from all areas within a given watershed. Hence till date all watershed monitoring & management studies in India were focused on only a few representative watersheds generally identified by means of the subjective methodologies, based on a collective judgment of a number of watershed characteristics. Further, most of the Indian watershed scale studies on soil and water conservation have revealed. Not only inadequacy of organization and skills are needed for collection and interpretation of data required for precise watershed planning but also reliance on intuition, engineering experience, thumb rules and/ or site specific simple techniques for making management decisions, even in this era with enough technology availability. Thus the present investigation was an attempt to develop a more conceptual Spatial Decision Support System (SDSS), comprising of a continuous scale SWAT hydrologic model linked to a ARC-View GIS system, for a test Nagwan watershed situated in the Damodar-Barakar catchment of D.V.C., Hazaribagh, Jharkhand. For demonstrating its potential to not only estimate water and sediment yields under prevailing resource management systems and but also to identify priority areas, having high potential for water and soil loss, within the test watershed. Application of the proposed SDSS on the test watershed revealed that it could predict average (annual) water and sediment yields values of 383.37 mm and 21.28 t/ha, as against the actual observed average (annual) water and sediment yield values of 390.69 mm and 25.35 t/ha respectively, for a 9 year validation period (1981-1983; 1985-1989 and 1991). It was further observed that these estimated and observed average annual water and sediment yield values were associated with good to moderately good correlation coefficients of 0.83 and 0.65; model efficiency coefficients of 0.54 and 0.70; mean relative errors of -4.28 % and -17.97% and root mean square prediction errors of 71.8 mm and 9.63 t/ha, respectively for the validation period. On further assessing the predictive potential of the proposed SDSS on monthly basis, it was observed that the proposed SDSS was associated with correlation coefficient, model efficiency coefficient and root mean square prediction difference (RMSPD) values of 0.72, 0.72 and 38.8 mm and 0.58, 0.42 and 4.29 t/ha, respectively for the monthly observed vs. predicted total water and sediment yields, respectively. The results thus clearly showed that the proposed SDSS could simulate the annual dynamics of the total water and sediment yields at the test watershed outlet reasonably well. The study further indicated that the proposed SDSS could be used as an efficient tool for prioritizing critically eroded areas within the test Nagwan watershed in Damodar-Barakar catchment and, when linked to a linear programming tool, could also be used for proposing, allocating and assessing the impact of optimum land use and conservation practice plans in the test watershed, for limiting it’s total soil loss within its soil loss tolerance value and increasing its crop productivity. Data Used:
Both Primary & secondary information on weather, hydrology, soils, land use and farming practicesHighlights/Findings:
The present investigation was an attempt to develop a Spatial Decision Support System (SDSS) for a test Nagwan watershed situated in the Damodar-Barakar catchment in India, the second most seriously eroded area in the world, for not only estimating sediment yields under prevailing resource management systems but for also designing a linear programming (LP) based optimized land use & conservation practice plans for soil loss reduction in the test watershed.
Validation of the proposed SDSS on nine (1981-1983; 1985-1989 and 1991)-year sediment yield data for the test watershed revealed that it could mimic the annual dynamics of the total sediment yields at the test watershed outlet with a correlation coefficient of 0.65; model efficiency coefficient of 0.70; mean relative error of -17.97% and root mean square prediction error of 9.63 t/ha and that it could be used as an efficient tool for assessing sediment yields from different parts of the test watershed and for designing a linear programming (LP) based optimized land use & conservation practice plans for reduced total sediment yields from the test watershed.
The LP based land use plan (Figure1
) although proposed no change in the total areas under paddy, corn and forest land use types yet it suggested their re-distribution within the test watershed thereby leading to not only a reduction in the test watershed’s total sediment yield by about 14.61%
) but also an increase in it’s paddy and corn crop productivity by 2.80 and 68.14 per cent, respectively. The proposed LP based land use plan for the test watershed could thus lead to an enhanced productivity benefit of about Rs. 3735/ha, in monetary terms, from corn crop cultivation at its optimal locations.
Both linear programming (LP) and simple watershed prioritization criteria based alternate conservation practice plans were designed for the test watershed using the sediment yields estimated by the proposed (validated) SDSS. Incorporation of these conservation plans into the proposed SDSS showed that LP based optimized conservation plan, implanted in 72 % of total watershed area, could lead to a maximum reduction (44.16 %) in the total soil loss from the watershed. This was followed by the prioritization criteria – 3, 2 and 1 based conservation practice plans, implanted in 51, 22 and 29 % of the test watershed area which lead to about 27.74, 15.15 and 12.05 per cent reduction in the total soil loss from the watershed. However, a simple Benefit: Cost analysis in terms of a few major (accountable) costs and benefits due to these conservation practice plans demonstrated that although the SDSS incorporation of the LP based conservation plan (in 72 % of total watershed area) can bring down the total soil loss from the test area quite close to its soil loss tolerance value (11.40 t/ha) yet it was slightly less economically feasible than implanting conservation practices in just 22% of the total watershed area (Table1
) Date of project completion:
Total Cost of Project:
Rs. 13,45,000Project investigator:
Dr (Mrs.) Ravinder Kaur,
Senior Scientist, Division of Environmental Sciences,
Indian Agricultural Research Institute, New Delhi-110012 (INDIA),
Phone: 011-26106695®; 011-25811112(o)