Abstract
Mountainous forested watersheds are important hydrologic systems that are responsible for much of the water supply and run-of-the-river hy-dropower schemes in many parts of the world. In India, the Western Ghats are one of such important hydrologic systems located in southern peninsular region. Several of these watersheds are ungauged. The Soil and Water Assessment Tool (SWAT) has been used to model streamflows for two mountainous forested watersheds, namely, Gurupur (699 km2) (a gauged watershed) and Upper Payaswini (44.6 km2) (an ungauged wa-tershed). Model calibration and validation are performed using monthly and daily streamflow data for the gauged watershed. Sample flow values obtained over a limited period were used for validation of ungauged wa-tershed. Flow duration curves (FDCs) have been derived to assess per-centile flow distributions. Model performance is evaluated using Nash-Sutcliffe coefficient (ENS), percent bias (PBIAS), coefficient of de-termination (R2) and comparison of percentile flow values obtained from observed and simulated FDCs. Sensitivity analysis with Latin Hypercube One-factor-At-a-Time (LH-OAT) indicates five soil-land use related pa-rameters namely, soil available water capacity (SOL_AWC), soil evapora-tion compensation factor (ESCO), soil depth (SOL_Z) and layers, groundwater baseflow (ALPHA_BF), and curve number (CN2 (forest & agriculture)), to be sensitive for simulating both gauged and ungauged wet mountainous forested watersheds. Study shows that lateral flows from dynamic sub-surface zones in such watersheds contribute substan-tially to the total water yield.
Highlights
Mountainous forested watersheds are important hydrologic systems that are responsible for much of the water supply and run-of-the-river hydropower schemes in many parts of the world [1] [2] [3]
The wet tropical Western Ghats mountain ranges in South India present an interesting combination of meteorological and physical characteristics that require an understanding of the catchment response and variability in water availability
The sensitivity analysis resulted in a list of parameters from most to least sensitive (Table 3) that includes soil, land use and groundwater parameters as discussed in subsequent sections
Summary
Mountainous forested watersheds are important hydrologic systems that are responsible for much of the water supply and run-of-the-river hydropower schemes in many parts of the world [1] [2] [3]. The hydrologic regimes of these forested high-elevation headwaters of Western Ghats are linked to streamflow processes in low elevation stream reaches and serve as inputs to water supply schemes and run-of-the-river mini, micro and small hydropower plants. To better simulate these linkages in the mountainous watersheds of Western Ghats, most of which are ungauged watersheds, there is a need to understand spatial and temporal variations in water availability. The wet tropical Western Ghats mountain ranges in South India present an interesting combination of meteorological and physical characteristics that require an understanding of the catchment response and variability in water availability
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