Hydrological studies for small watershed in India using the ANSWERS model

A study was undertaken with the objective of investigating the performance of the physically based distributed parameter Areal Non point Source Watershed Environment Response Simulation (ANSWERS) model for a 16.13 km2 small watershed in eastern India by using digital elevation model (DEM), GIS and remote sensing techniques for automatic extraction of the model input parameters. The model was calibrated by using sixteen storms of 1993 and 1994 and validated with fifteen storms of 1995 and 1996. For calibration storms, the model simulates surface runoff, peak flow and sediment yield with average per cent deviation (Dv) equal to −9.32, 1.24 and −3.04 and coefficient of efficiency (E) equal to 0.964, 0.881 and 0.884 respectively. For validation storms, the model simulates surface runoff, peak flow and sediment yield with average per cent Dv as −8.13, −2.25 and −1.63 and E as 0.991, 0.741 and 0.965 respectively. During model calibration and validation the peaks of the simulated hydrographs for majority of the storms were found to occur after the peaks of the observed hydrographs. The statistical comparisons indicate that the model simulates runoff, peak flow and sediment yield well for most of the storms with Dv less than 15% from the observed values and average value of E greater than 0.80. The model calibration and validation results indicate that the ANSWERS can be successfully used for simulating the watershed response under varying soil moisture and watershed conditions. The study reveals the suitability of the ANSWERS model application for the other Indian watersheds of similar hydro-geological characteristics.