Model of Surface Water Management Based on the Potency of Water Balance

Abstract

Purpose: This research intends to build the simulation model of surface water management in the Kali Lamong watershed based on each water district for maintaining in order to be able to fulfill the sustainable water demand   Theoretical reference: Management of surface water is one of the very important issues nowadays. By the climate and land use change, it is adding the water resources problem in the future. Kali Lamong watershed is one of water sources for Surabaya city and the other cities. Water availability in Lamong watershed becomes very important to be known, and how is the condition in the future on short term (2050), medium term (2075), and long term (2100) by using the three scenarios for facing the uncertainty.   Method: The methodology consists of developing the model of water management based on the water district by integrating the simulation result into the solutions for developing water management for reaching the water safety in the Kali Lamong watershed.   Result and Conclusion: The simulation result shows that on the condition of scenario A, there is needed the reservoir capacity in short term (2050) in Lamong Hulu and Kalitemu that is 18 and 8 million m3; for medium term (2075) is 35 and 19 million m3; and for long term (2100) is 62 and 34 million m3. For scenario B, there is needed the reservoir capacity for short term (2050) in Lamong Hulu and Kalitemu is 23 and 10 million m3, for medium term (2075) is 35 and 15 million m3, and for long term (2100) is 50 and 26 million m3. However, for scenario C is needed the reservoir capacity for short term (2050) in Lamong hulu and Kalitemu is 26 and 11 miliion m3, for medium term (2075) is 45 and 21 million m3, and for long term (2100) is 80 and 38 million m3.   Implication of research: Based on the prediction result of rainfall and land cover change, there is obtained the dependable discharge (Q-80%) in each water district with 3 scenarios including the projection of water demand. The potency of water balance in each water district produces 3 water districts which experience water deficit in Lamong Hulu, Sabeng, and Kalitemu Water District. To fulfill the water deficit in water district, there is carried out by building reservoir in the watershed downstream in two locations that are Lamong Hulu and Kalitemu water districts and it is integrated in the water management model.   Originality/ value: To build a simulation model of surface water management.