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.
