INTEGRATED WATER RESOURCES MANAGEMENT OF A RIVER STRETCH USING GIS AND GROUNDWATER FLOW MODELING

Abstract

The Himalayan areas face frequent occurrence of water scarcity. Thus, there is a need for an assessment of water resources of the region. Based on the assessment of existing water resources and new potential water bearing zones, need to be studied to meet the water needs of the population. Due to high seasonal variability in river flows and very high sediment transport and monsoonal turbidity in river water in mountainous areas, indirect surface water abstraction form river bank for drinking water production is becoming a cost effective and sustainable alternative to the direct abstraction of river water and associated - conventional treatment. However, the identification of suitable sites for indirect surface water abstraction is problematic due to limited vertical and horizontal extent of alluvial deposits. For an economical identification of potential sites, an approach combining various non-invasive techniques using geographical information system (GlS), remote sensing and groundwater flow modeling (PMWin) software, has been developed for a study area comprising a 100 km long mountainous stretch of the Alaknanda River in the state of Uttarakhand, India, having a catchment area of 10577 km2. In the river stretch, total water availability is 50045 MLD and total water demand is assessed as 88 MLD. Out of total water demand, agricultural water demand is 57 MLD and drinking water demand is 31 MLD and gap of 17 MLD computed for river stretch area. From surface water 8 MLD water is abstracted from in directed surface water scheme. Currently only 3.5 MLD waste water is collected for treatment at Srinagar. It has been noticed that some hand pumps and wells are contaminated by nitrate, pH, iron, etc., can be utilized for agricultural purposes. The potential locations of alluvial deposits were identified by generating thematic GIS maps of land use, terrain and geology, using a weight-age factor. The sites thus identified were characterized using groundwater flow modeling for their optimal abstraction rate, travel time and flow field of the induced bank filtrate. The purification capacity of the aquifer was estimated for the removal of organic micro-pollutants (OMP) using the SOMA-tool and was correlated with the river meandering sinuosity (S). Along the 100 km river stretch, 8-9 locations were found suitable for indirect p IV I P a g e surface water abstraction. An S-value of around 1.4 resulted in the highest purification capacity and a bank filtrate portion of 44-1 00 % in the abstracted water from 14 wells located 75 m from the riverbank under the defined conditions. The calculated removal of different OMP was 26-91 %. Based on cost comparative analysis, indirect surface water abstraction schemes were found about 10-14 times cheaper than direct surface water abstraction schemes in the region. The estimated water production capacity for one of the site is computed 16,800 m3/day by using mudflow software. Based on this study, around 30 potential RBF sites were identified in seven large towns and cities Rishikesh, Ramanager, Haridwar, Dehradun, Roorkee, Kotdwar and Haldwani having a total population of 1.23 million situated in the flood plains in the Himalayan area.