Temporal Variation of Tropical Karst Groundwater Suitability for Irrigation in Gremeng Resurgence, Gunungsewu Karst Area, Indonesia

Abstract

Analysis of groundwater availability for irrigation purposes pertains to not only quantity but also quality. The characteristics of groundwater quality essentially define crop productivity and determine whether or not crops can grow. This research was designed to identify the suitability of karst groundwater for irrigation temporally (in one year), with an example of Gremeng Resurgence in Gunungsewu Karst Region, Indonesia. It drew on data on electrical conductivity and several major ions, such as potassium, magnesium, sodium, and calcium, by analyzing % sodium content (Na%), Sodium Adsorption Ratio (SAR), and groundwater suitability for irrigation using the Wilcox and USSL diagrams. These analyses revealed that the water quality observed varied by seasons owing to the effects of dilution by rain and water-rock interaction in the karst region. However, this temporal variation was not substantial so that the classes of groundwater suitability only ranged between good and excellent, and the salinity hazard levels differentiated into low until medium.