Analysis of Developmental Scenarios in Ganga River Basin using a Strategic River Basin Planning Tool (GangaWIS)

Abstract

The Ganga River basin is the most populated river basin in the world and almost half of the population of India is living in this basin. The Ganga basin outspreads in India, Tibet (China), Nepal and Bangladesh over the total area of 10,86,000 Sq.km. The major part of the geographical area of the Ganga basin lies in India and it is the biggest river basin in the country draining an area of 8,61,452 Sq.km. It covers states of Uttar Pradesh, Madhya Pradesh, Rajasthan, Bihar, West Bengal, Uttarakhand, Jharkhand, Haryana, Chhattisgarh, Himachal Pradesh and Delhi. As per the reports average water resources potential of Ganga basin is 525 BCM. The Ganga basin has a vast reservoir of groundwater, replenished every year at a very high rate. The mean annual replenishable groundwater in Ganga basin is about 202.5 billion cumec per annum.The health of the Ganga basin is deteoriating significantly due to increase in population, high level of water stress due to abstraction of water for increasing agricultural, industrial and domestic uses, and pollution in the river. The major water resources challenge in the Ganga basin is to judiciously manage the water resources to fulfil the ever-increasing agriculture, domestic, and industrial water demands without harming the eco-system. About 77% of the population in the basin is engaged in agriculture which is mostly dependent on irrigation, as almost 85% of rainfall in the basin takes places in four monsoon months from June to September. To deal with such a large and intricate river basin, a tool named GangaWIS (Ganga Water Information System), which is based on Deltares model FEWS (Flood Early Warning System) and developed recently, has been used in the present study to analyse the integrated impact of different possible management strategies on the basin water resources. GangaWIS is a comprehensive tool that integrates various hydrological components of the Ganga River basin and supports the policy makers in analysing the impact of various future developmental and climate change scenarios and possible interventions. It describes the functioning of water system of the Ganga basin within India with respect to rainfall-runoff, surface water and groundwater flow, storage and diversion of water for various purposes, water quality and ecology. The model simulates the present situation with respect to water resources, infrastructure and water demand. The water information system serves to store and disseminate all relevant information for planning, i.e. maps, measurements and input and output of the river basin model. A dashboard depicts the various indicators to judge the impact of the different scenarios, such as state of groundwater development, lowest discharge, volume of water stored in reservoirs, agricultural crop production, deficit irrigation and drinking water, surface water quality index, volume of groundwater extracted and ecological, hydrological and socio-economic status. The interaction between surface and groundwater is included in the model concept. GangaWIS can be used to analyse and visualise various data (temporal/spatial) and model result and it can provide relevant measured and modelled information to various users such as data managers, modelers and policy makers. Ganga river basin model is capable of assessing the impacts of future developmental/climate change scenarios and various interventions/measures at basin scale by comparison of simulation results. The scenarios are used to describe model input that approximates the expected situation so that the model output provides a simulation of the river flows, water quality aspects, and groundwater levels. The model inputs include land use, infrastructure development, population/industry/agriculture settings as well as the precipitation and temperature settings. In this study, the indicators of around 20 scenarios simulated by the Deltares in their study (Bons, 2018) were analysed and some of the interventions that can be immediately implemented in the field were identified. Some such interventions include a) implementing approved infrastructure plans, b) conjunctive use management in some irrigation commands, c) increasing irrigation efficiency by 10% etc. The model runs were taken to see the integrated impact of these interventions in achieving better utilization of water resources. The results obtained have been compared with the indicators analysed in the report and will be presented in detail in the paper. The results give a deep insight to the water resources issues in the basin and the impact analysis of various planned interventions. The findings of the study can be useful to the decision makers and different stakeholders in the basin. This analysis helps in visualizing the utility of GangaWIS tool to support strategic basin planning and can be continuously updated with improved data and better interventions.