Use of Forest Index or PLANOBAY in Estimation of Water Availability Due to Climate Change

Abstract

The present study tried to estimate future water availability with the help of Forest Index or Plantation-Prioritized Basin Yield Estimation (PLANOBAY) Hydrologic model, which is a multi-event, discharge prediction model based on variation of discharge with basin area and canopy cover. RCM-PRECIS model was applied to generate future weather scenarios. The observed rainfall along with Vegetated Area Index (VAIn) was used as input to estimate basin runoff. Presence of vegetated area (forest, plantations, cropped land) in any basin would impact the quantity of basin runoff as vegetated areas could hold water with greater capacity than any nonvegetated area. Hence the estimation of runoff from vegetated and nonvegetated catchment must differ and for former, models must include or consider the relationship between vegetated area and the amount of basin runoff. In PLANOBAY, VAIn represents the relationship between vegetated area and basin runoff. VAIn represented the variance of basin area and vegetated area with respect to basin runoff. A neurogenetic model was developed to identify the patterns associated with VAIn, rainfall, and basin runoff. Dataset of 3 decades (1970–2002) was employed to train the model. After the successful completion of training, models were compared with three conceptual models, namely, Hydrologic Engineering Centre – Hydrologic Modeling System (HECHMS), Trend Research Manual of 1955 (TR55), and MODified RATional (MODRAT) hydrologic model. The better model among the four was identified with the help of root mean square error (RMSE), correlation coefficient (r), coefficient of efficiency (E), and first-order uncertainty analysis (U). Future water availability was estimated with the help of estimated stream flow from the selected model, estimated rainfall from PRECIS climatic model-generated weather scenarios, and Water Budget equation. According to the results, PLANOBAY model was selected as better model among the four, and according to the estimations from the same model, future water availability of the two river basins would reduce for both A2 and B2 scenario of climate change where the water scarcity would be more pronounced in A2 than in B2.