Hydrology and water allocation in Malaprabha - comprehensive database and integrated hydro economic model for selected water services in the Malaprabha river basin

The study found that during the dry season extensive irrigation extraction in some zone resulted in drastic reduction in the inflow to Malaprabha reservoir

 malaprabhaThis study by CISED and NIVA aimed at the development of a comprehensive database on the status of water sector and the development of integrated hydro economic model for selected water services in the study area of the Malaprabha basin. The study focused on exploring the feasibility of Payment for Watershed Services (PWS) to improve the water availability through a detailed analysis of the historic hydrologic data and development of a framework of hydrologic and water allocation model. A hydro-allocation model was developed using the software - ArcView SWAT (AVSWAT) and MIKE-BASIN models.

Terrain characteristics, land use and land cover, soil characteristics, crop characteristics and yield, hydro-meteorological data, stream flow and reservoir water level information were collected from various sources and assimilated in the database. Objectives of the hydro-allocation modelling was to set up a catchment-scale model to simulate core hydrologic processes, develop different land use scenarios to assess the impact of land use changes on the stream flow, and carry out the optimum allocation of water among irrigation and drinking water uses as well as among various geographical areas within the irrigation sector.

From the studies carried out, it was found that MIKE-BASIN could not prioritise the water allocation within a single sector i.e., irrigation across different crops across different areas. Consequently, it could not be applied to obtain an optimum water allocation scenario in the Malaprabha catchment. From the study, it was found that extensive irrigation extraction in zone-2 and zone-3  resulted in drastic reduction in the inflow to the Malaprabha reservoir, especially during the dry season.

Due to the evaporation and transmission losses along the channel, it was concluded that for the economic benefit from one cubic meter of water, crop yield in the command area may have to be up to several times that in the upper catchment, assuming cropping pattern, prices and farming costs are similar in the command area and in the upstream catchment.

A calculated example showed that upstream-downstream water trading, if it were possible from an institutional and technical point of view, would not be economically feasible during June-October (due to surplus water supply) and March-May (due to water scarcity). From the analysis, economic water trade was found feasible during the period November-February if yield at downstream was more than that at upstream.

This report has been prepared as part of the India-PES initiative, which was a collaborative effort undertaken on a pilot basis, by CISED and NIVA, for the development of integrated tools and consulting services for Watershed Management and 'Payments for Environmental Services' (PES) in India. Tools and methodologies developed as part of this initiative were tested in the Malaprabha river basin in the state of Karnataka, and the PES implementation was focussed on Participatory Irrigation Management. For more info on this initiative, please click

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