Bhadra Command Area is located in a semi-arid zone and is one of the most important agricultural areas in Karnataka. Due to the scarcity of water resources, the water use efficiency in this sector stands very low. This makes it important to determine the amount of available fresh water for agricultural uses and recommend a sustainable method of optimal water use for crops especially for paddy. The book aims at how much water is necessary, especially for major paddy growing areas and also to know the loss of water through percolation and evapotranspiration. An accurate measurement of evapotranspiration (ET) could lead to the development of improved water use efficiency. Traditional ET measurements using lysimeter is accurate but time consuming and laborious. The Surface Energy Balance Algorithm for Land (SEBAL)algorithm gives a reasonable actual evapotranspiration with a small amount of ground data.