Water conservation measures and cropping pattern for a watershed using geospatial techniques and SWAT modelling

Abstract

The Manali watershed located in Thrissur district of Kerala with a drainage area of 140.94 km 2 receives an average annual rainfall of 2501.08 mm. But the watershed experiences increased water level rise during monsoon and scarcity of water during non-monsoon season. In order to address the problem of water scarcity in the watershed, an attempt was made to plan conservation measures and cropping pattern using geospatial techniques and SWAT modelling. SWAT model was used effectively for the hydrologic water balance assessment and water availability in the watershed. Water demand was estimated as the sum of agricultural and non-agricultural water demand. Agricultural water demand was estimated using CROPWAT 8 model. An analysis of monthly water availability and water demand was carried out to know the status of water in the watershed. Site suitability modelling was done using GIS to locate water conservation measures and IMSD guidelines were applied to select the type of water conservation measures. Cropping pattern was proposed based on existing crops, soil type, physiography and aridity index. The model was calibrated and validated satisfactorily for the watershed with NSE values 0.71 and 0.61 and R 2 values 0.81 and 0.61 during calibration and validation respectively. The highest water availability (71.57 Mm3) was found in the month of June and lowest (1.28 Mm3) in the month of January. Water demand was highest in the month of January (8.91 Mm3) and lowest in the month of June (1.23 Mm3). Water surplus was observed in almost all the months of the year except January, February, March and December. The annual total water surplus in the watershed was obtained as 227.43 Mm 3 . Hence conservation measures were proposed for the watershed. Thus 32 farm ponds, 7 percolation ponds and 4 check dams were suggested to construct in the watershed area. Farm ponds were found to be the most suitable conservation measure in the area. Suitable cropping pattern like sequential cropping and intercropping were also suggested to improve the productivity and economic status of the watershed.