CS(AR)-1/2014 : Water availability study and supply demand analysis in Kharun sub-basin of Seonath basin in Chhattisgarh state

Abstract

The present Purpose Driven Study (PDS) deals with addressing and resolving various hydrological issues of the Chhattisgarh state to tackle the problem of increasing water demands and water scarcity being faced by state. In present study the hydro-meteorological, agricultural and demographic data of the Kharun river basin was analyzed using different technique to carry out the rainfall runoff modeling, water availability study and water supply-demand analysis. In this study, the MIKE BASIN model for Kharun river was developed to study the hydrological behavior of the river. It was observed that the Kharun is originally an intermittent river having no flow during lean season, moreover there has been no water storage structure at the upstream. To tackle the situation, the Kharun river is being supplemented from Ravishankarsagar reservoir through canals to meet various water demands and water supplied for various usages through the series of anicuts. Thus the flow regime in Kharun has been found strongly influenced by regulation operations associated with the river.

The drought study indicated that the Kharun river basin on an average experiences 2 drought years in every 10 years period which were mostly of moderate nature. The low flow analysis indicated that the Kharun river generally experiences 1 or 2 low flow condition every year. The low flow events in this basin usually begin during July to October and terminate during November to December and it can be the matter of concern for water resource planning and allocation in the basin. The Rainfall-Runoff Modeling was carried out using MIKEll NAM model in the Kharun river using observed discharge at Patherdihi gauge discharge site. The coefficient of determination (R2) values of model calibration and validation were observed 0.858 and 0.764 respectively. It indicated the good agreement between the simulated and observed catchment runoff in terms of the peak flows with respect to timing, rate and volume. Thus the model can be used for predicting the runoff time series for the extended time period in the Kharun basin and it can also be used for predicting runoff time series of another basin of similar characteristics. The Efficiency of the model was obtained as 81% which shows that the choice of the model parameters was relevant.

The water availability analysis indicated that the Kharun river is originally an intermittent river having flow during monsoon season and 2-3 months thereafter. The average annual rainfall of 1147.57 mm produces 1802.88 MCM of average annual runoff in Kharun. The Ravishankarsagar reservoir and other sources add around average 116.22 MCM water in to the Kharun river and the average annual regulated flow becomes 1919.1 MCM which is supplied to meet various water demands. The water from Kharun river is being utilized mainly to meet domestic and industrial water demand. If the water supply was planned at 90% probability level, the total water demand was observed 65 MCM in 2010-11 and the deficit was 22 MCM. When the demand would increase to 133 MCM (in 2030-31) and 175 MCM (in 2050-51) the water deficit would becomes 73.56 MCM and 105.33 MCM respectively. In year 2050-51, the additional 105.33 MCM water would be required in Kharun river to fulfill the total demand. The surplus-deficit

analysis indicated that, during a water year the period of water deficit prolongs if assured water availability is planned at higher probability level. As the water demand increases, the water deficit period increases and the river starts experiencing the water deficit much earlier. The study was also carried out for identification of possible storages sites on Kharun river, their submergence area and possible storage capacities. Four best possible dam sites were identified on Kharun river basin for construction of small storage structure using DEM data which would help to meet the future water demand in the basin. The derived Area-Elevation-Capacity curves of the proposed sites would be useful during construction of dam. It was recommended that the water storage in these tanks should be planned to minimize the submergence effect and to create structure of adequate storages. The infiltration tests were conducted at nine selected sites in Kharun river basin using double ring infiltrometer. The infiltration rate was observed varying from 0.4 to 4.3 cm/hr in Kharun river basin. The regional infiltration models were developed for different soil type and for a Kharun basin as a whole. The regional infiltration model based on the Phillip's two-term model was found best suited for the Kanhar soil. Kostiakov's and Green-Ampt model could be applied for modeling the infiltration rate of Matasi and Sandy-murrum soil. However the regional model based on Green-Ampt model was found best for simulating the infiltration rates for the whole Kharun basin.

On the basis of various hydrological analyses carried out, some of the key recommendations were arisen for the water resources development, management and its optimum utilization in Kharun basin. Though the occurrence of droughts is not a big threat in the region, water crises in rural as well as urban areas during every summer has become common in the state. Hence there is an urgent need to tap the river water which is being drained down causing more dependence on groundwater in the region. The mechanism has to be developed for regular monitoring and assessment of water demands and water availability to meet future challenges. It is recommended that the state WRD should maintain adequate hydro-meteorological data monitoring network which is the key for long term planning of water resources of river basin. To meet the local water demands, state should plan for construction of small dams on Kharun river. The water resources planning should includes issues such as demand management in the river basin, planning of water supply at appropriate level of probability and providing assured water supply to meet demands. WRD should adapt scientific approach like hydrological modeling and use of modern softwares for planning purposes. There is a need to undertake regular awareness programs for field engineers, various water users and stakeholders for judicious use of precious water resources.