Water balance model aided in estimating net groundwater inflow at Lake Maninjau, West Sumatra - Indonesia

Abstract

Sustained lake functioning requires proper catchment land and water management. To address this, quantitative information and comprehensive understanding of the spatiotemporal dynamics and hydrological budget of the lake ecosystem are required. However, measuring hydrologic components such as groundwater discharge into a freshwater body is difficult, since its direct measurements are costly, time-consuming, and hardly implemented. Therefore, this study was intended to quantify groundwater inflow to the lake through an effective approach using the water balance modeling technique. Herein, groundwater discharge and contribution were calculated as the water balance residual in terms of net groundwater inflow. It can be considered a minimum estimate of groundwater inflow, as there the groundwater outflow maybe exists but not quantifiable. The approach has been applied for Lake Maninjau which is categorized as a deep, regulated, and tecto-volcanic lake located in West Sumatra Province, Indonesia. The result indicates that the groundwater inflow slightly moderately influences the fluxes of new water volume (the region between observed lowest and highest lake water level) at the upper layer of Lake Maninjau. Its contribution was equivalent to at least 20-28% according to the assessment for the years of 2013 and 2014. Annually, the new water volume recharged from the groundwater inflow corresponded to at least 182-281 million m3. Moreover, these findings enhance a previous study stated that the terrain system of Lake Maninjau is dominated by a rare groundwater aquifer.