Ecology, Environment and Conservation Paper

MODELLING IMPACT OF CROPPING PATTERN AND URBAN AREAON GROUNDWATER RESOURSES OF NAGARJUNA SAGAR RIGHTCANAL COMMAND AREA USING VISUAL MODFLOW

R. Ganesh Babu, G. Ravi Babu, A. Mani, P. Prasuna Rani and V. Srinivasa Rao

Abstract

Groundwater models can be used for the assessment of the impact of the different cropping pattern andchange in urban area on groundwater resource and modeling is the best tool to optimize the differentcombinations or scenarios and to select the best combination or scenario for management of sustainablegroundwater resources. In this study, three-dimensional finite-difference groundwater model VisualMODFLOW 2.8.1 was used to simulate the groundwater dynamics in Nagarjuna Sagar Right CanalCommand area. The net area irrigated under Nagarjuna Sagar Right Canal is 4.75 lakh ha. Calibration andvalidation of the model has been carried out and used to predict the static groundwater storage availabilityin the study area for different cropping pattern scenarios and change in the urban area. The validatedVisual MODFLOW 2.8.1 was used to simulate the groundwater dynamics in the study area for the years2030 and 2040 with different cropping pattern scenarios and change in the urban area. Global climatemodel MarkSim, which is developed by the International Centre for Tropical Agriculture (CIAT) was usedto generate future weather data for the years 2030 and 2040. The impact of change in cropping pattern onstorage of static groundwater resource in the study area for the years 2030 and 2040 was assessed with twoscenarios of change in rice cropped area decreased by 50 per cent and 100 per cent with this cropped areacultivated equally by the ID crops. These results showed that the lesser storage of static groundwaterresources in future lesser. The change in the cropping pattern affects the net recharge of the groundwaterwhich influences the groundwater levels. Increase in paddy area increases the recharge and rise ingroundwater level has been identified. In the study area, cropping pattern could be changed from rice cropto other irrigated dry crops to prevent the increase of groundwater resources which leads the water loggingcondition in the study area. The urbanization is one of the most significant factor considering for assessmentof the response on the groundwater levels and availability of static groundwater resources. The groundwaterrecharge is very less in case of increase in urban area and generates more runoff rather than the intake ofrainfall in the ground surface as having the impervious nature. In view of increase in urban area in thestudy area, the four scenarios are proposed with the combination of 10 per cent and 20 per cent decrease inrecharge and 50 per cent and 100 per cent increase in groundwater draft and simulated the groundwater fluctuations for the years 2030 and 2040. The impact of change in the urban area on storage of availablestatic groundwater resource in the study area for the years 2030 and 2040 was assessed with four scenarioscombination of groundwater recharge and groundwater pumping. The storage of static groundwaterresources would be expected in future lesser than the present storage of static groundwater resources in allscenarios due to increase in urban area as increased in impervious nature of the ground surface. The declinein available static groundwater resources would be expected 6.38 per cent and 7.08 per cent during 2030and 2040 respectively. The rapid expansion in the urban area and their settlements is also one of the reasonsfor the depletion of groundwater resources with low recharge and high groundwater draft.