Because rainfall in the coastal area is high and water projects are nearly missing, we think it is important to make use of available water resources. In order to predict future rainfalls and suggest proper management of resources, we created a mathematical model linking rainfall amounts between demand (population, agricultural and industrial) on water resources during the period (2000-2012). Results show the following: 1. Rainfalls decreased during the period ( 2002-2012) at an annual rate of (1.84%). 2. Demand on water resources increased during the period (2002-2012) at an annual rate of (3.41%) of the population demand, and (3.47 %) of the agricultural demand, and 6.25% for industrial demand. 3. There is a surplus of available water resources and the size of demand for them, with the surplus decreasing during the period (2002-2012) at an annual rate (2.97 %). 4. The estimation of the surplus between the amount of available water resources and the size of the demand for them will decrease in 2023 from what it was like in the year 2013 at an annual rate (-3.23%).