Simple hydrologic model for predicting streamflow in small watersheds for irrigation system planning

Abstract

© 2016, Asian Association for Agricultural Engineering. All rights reserved. A simple and easy-to-use hydrologic model was developed for predicting streamflow in small watersheds in the Philippines for irrigation system planning purposes. The hydrologic model is a lumped-parameter type with four parameters that are optimized and five parameters that can be fixed. It uses daily rainfall and potential evapotranspiration as inputs and generates daily and mean monthly streamflow or runoff as outputs. It was tested in six small watersheds in the Philippines, ranging in area from 24 to 879 sq. km and located under different climatic types. The model generally performed well for small watersheds with a catchment area of up to 128 sq. km, adequately capturing the temporal behavior of streamflow. Model calibration and validation generally yielded acceptable values of the standard statistical criteria for assessing the goodness-of-fit such as Nash-Sutcliffe model efficiency (NSE>0.5), root mean square error (RMSE< 3.0 m3/s), percent bias (PBIAS< ± 25%) and ratio of RMSE to the standard deviation of observed data (RSR<0.7). Based on low flow comparison, the NSE further increased while the RMSE, PBIAS and RSR decreased during model calibration and validation for the small watersheds, indicating the model's strength in predicting baseflow, which is critical in dependable flow estimation. Sensitivity analysis showed that only two of the four model parameters are highly sensitive. Model application was demonstrated for flow augmentation during a period with recorded climate variability sequences. The application of this simple hydrologic model may be further extended to other small watersheds in the Philippines and in other countries with similar hydrologic and climatic conditions. Ultimately, this model can serve as an alternative tool for irrigation system planning, design and development.

Source or Periodical Title

International Agricultural Engineering Journal

ISSN

8582114

Page

2013-01-01

Document Type

Article

Subject

Dependable flow, Flow augmentation, Hydrologic modeling, Irrigation system planning, Small watersheds

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