Water resources engineering is the quantitative study of the hydrologic cycle— the distribution and circulation of water linking the earth’s atmosphere, land, and oceans. The main sources of water supply are surface and ground water which have been used for a variety of purposes such as drinking, irrigation, hydroelectric energy, transport, recreation, etc. Often, human activities are based on the usual or normal range of river flow conditions. Flows and storage vary spatially and temporally, and also they are finite in nature that is there is a limit to the services that can be expected from these resources. Rare or extreme flows or water quality conditions outside the normal ranges will result in losses to river-dependent, human activities. Therefore, planning is needed to increase the benefits from the available water sources. Poor quality water and unsustainable supplies limit national economic development and can lead to adverse health and livelihood conditions.