Optimization Models for Sustainable Utilization of Groundwater in Wajo District, South Sulawesi Province of Indonesia

Abstract

The groundwater in Siwa-Pompanua basin of Wajo Regency has a coverage area of 93,900 ha and a potential debit of 379 millions m31yr. The groundwater has been utilized since 1995 to irrigate rice fields managed by farmers themselves. Since then number of wells has been increased rapidly and randomly distributed and at the present time there are 16 units covering 232 ha of rice fields. There are still high trends that the number of wells would increase. Without well understanding and proper management of the groundwater it is easy to witness that many problems have been accumulated. These problems are not only physical but also social as well as threatening the environment that would affect the availability of the ground water. Thus, it is timely important to find a way out to solve the problems based on basic knowledge so the utilization of the groundwater is sustainable. This study aims at optimizing the utilization of groundwater for irrigating the rice fields with taking into account socio-economical and environmental aspects. Herewith, mathematical models were developed based on the water flow equations, crop water requirement and combined with socio-economical analysis and preventing degradation of the aquifers. The water flow model was compared to measured data and resulted in a good conformity. Based on the daily water requirement of 46 m3'ha and with preventing excessive drawdown, the optimum discharge of each well differs with the others. Its values are between 279 m3/d and 1268 m3/d and the command areas range from 10 ha to 28 ha, respectively. A neighboring well should be in the radius of about 479 m away. In the average, farmers would gain an extra income if they manage the groundwater in this sustainable way.