Development, Test and Validation of A Data Intensive Spatial Decision Support System (SDSS) for Runoff Simulation and Design Hydrograph Generation - A Case Study

Abstract

A data intensive Geomorphic Instantaneous Unit Hydrograph (GIUH) technique based Spatial Decision Support System (SDSS) for runoff simulation and design hydrograph generation has been developed for ungauged or inadequately gauged watersheds. The application potential of the developed SDSS for runoff simulation and design hydrograph generation for 2, 5 10 and 25 years return periods was tested on a (gauged) second order (test) agricultural micro-watershed in Almora district of Uttranchal state in India. The overall Root Mean Square Error (RMSE) associated with the SDSS simulated run-off rates was around a moderate value of 0.0023 m3/s. Out of the 51 test storms simulated, about 50 °A of simulated hydrographs were associated with well predicted total and peak runoff volumes. Besides this, 30 hydrographs had good shapes and 10 hydrographs were associated with peak runoff times synchronized with their observed values. Analysis of the effects of storm-season, size, duration and their combinations revealed that this was majorly due to the incapability of the conventional rainfall excess determining SCS-CN method to account for the within-storm moisture changes. Sensitivity analysis of the subjectively assessed SDSS input parameters on a test (summer season) storm indicated that curve number is the most sensitive input parameter and that it should be carefully parameterized for best SDSS performance.