Hydrology of inland tropical lowlands: the Kapuas and Mahakam wetlands
H. Hidayat1,2, A. J. Teuling1, B. Vermeulen1, M. Taufik1,7, K. Kastner1, T. J. Geertsema1, D. C. C. Bol1, D. H. Hoekman3, G. S. Haryani2, H. A. J. Van Lanen1, R. M. Delinom4, R. Dijksma1, G. Z. Anshari5, N. S. Ningsih6, R. Uijlenhoet1, and A. J. F. Hoitink11Hydrology and Quantitative Water Management Group, Wageningen University, Wageningen, The Netherlands 2Research Center for Limnology, Indonesian Institute of Sciences, Cibinong, Indonesia 3Earth System Science and Climate Change Group, Wageningen University, The Netherlands 4Research Center for Geotechnology, Indonesian Institute of Sciences, Bandung, Indonesia 5Soil Science Department, Tanjungpura University, Pontianak, Indonesia 6Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Bandung, Indonesia 7Department of Geophysics and Meteorology, Bogor Agricultural University, Bogor, Indonesia
Received: 01 Aug 2016 – Accepted for review: 19 Aug 2016 – Discussion started: 23 Aug 2016
Abstract. Wetlands are important reservoirs of water, carbon and biodiversity. They are typical landscapes of lowland regions that have high potential for water retention. However, the hydrology of these wetlands in tropical regions is often studied in isolation from the processes taking place at the catchment scale. This contribution offers a comprehensive analysis of the hydrological dynamics of two neighbouring poorly gauged tropical basins; the Kapuas basin (98,700 km2) in West Kalimantan and the Mahakam basin (77,100 km2) in East Kalimantan, Indonesia. Both basins are characterized by vast areas of inland lowlands. The hydro-climatological data described herein were obtained during fieldwork campaigns carried out in the Kapuas over the period 2013–2015 and in the Mahakam over the period 2008–2010. Additionally, we used the Tropical Rainfall Measuring Mission (TRMM) rainfall estimates over the period 1998–2015 for analysing the distribution of rainfall and the influence of El-Niño – Southern Oscillation. Flood occurrence maps were obtained from the analysis of the Phase Array L-band Synthetic Aperture Radar (PALSAR) images of 2007 through 2010. Drought events were derived from time-series of simulated groundwater recharge using time series of TRMM rainfall estimates, potential evapotranspiration estimates and the threshold level approach. The Kapuas and the Mahakam lakes region are vast reservoirs of water of about 1000 km2 and 1500 km2 that can store as much as 3 billion m3 and 6.5 billion m3 of water, respectively. These storage capacity values can be doubled considering the area of flooding under vegetation cover. Discharge time-series show that backwater effects are highly influential in the wetland regions, which can be partly explained by inundation dynamics shown by flood occurrence maps obtained from PALSAR images. In contrast to their nature as a wetland, both lowland areas have frequent periods with low soil moisture conditions and low groundwater recharge. The Mahakam wetland area regularly exhibits low groundwater recharges, which may lead to prolonged drought events that can last up to 13 months. It appears that the Mahakam lowland is more vulnerable to hydrological drought leading to fire occurrence than the Kapuas basin.
Hidayat, H., Teuling, A. J., Vermeulen, B., Taufik, M., Kastner, K., Geertsema, T. J., Bol, D. C. C., Hoekman, D. H., Haryani, G. S., Van Lanen, H. A. J., Delinom, R. M., Dijksma, R., Anshari, G. Z., Ningsih, N. S., Uijlenhoet, R., and Hoitink, A. J. F.: Hydrology of inland tropical lowlands: the Kapuas and Mahakam wetlands, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-388, in review, 2016.