Dear Getachew,

Please, see the page of EPA:

 http://www.epa.gov/epahome/data.html

And  this paper:

Integrated Water Resources Optimization Models: An Assessment of a Multidisciplinary

Tool for Sustainable Water Resources Management Strategies

http://www.geo.mtu.edu/~asmayer/yaqui/geo_compass.pdf

Regards,

Vanessa

Climate change have both impact on coastal water, surface water and ground water. Different scientists use different models base on available data and case study area. I hope you may need to focus on some case(case study area), so selection is highly depending on it. Climate change impact on water resources always coupled with water pollution as well, you need to be very careful to differentiate these two and remove the pollution parameter from it. Your works seems rather tough work, but your findings might be a good study, if you try it with IPCC climate change scenarios.    Good Luck!