Assessment of Hydrological Alteration from 1996 to 2017 in Brantas watershed, East Java, Indonesia

Abstract

Climate, land use, and land cover change can propagate alteration to the watershed environment. The interaction be- tween natural and human activities probably accelerates the change, a phenomenon that will generate serious environmental problems. This study aims to evaluate the change in the hydrological regime due to natural and human-induced processes. The study was conducted in Brantas watershed, Indonesia, which is the largest watershed in East Java. This area is populated by more than 8 million inhabitants and is the most urbanized area in the region. An analysis of rainfall time series use to

shows the change in natural phenomena. Two land-use maps at different time intervals were used to compare the rapid development of urbanization, and the discharge from two outlets of the sub-watersheds was employed to assess hydrological

changes. The indicator of hydrological alteration (IHA) method was used to perform the analysis. The daily discharge data

are from 1996 to 2017. The research results show an increase in flow (monthly, 1-day, 3-day, 7-day, 30-day, and 90-day

flows) in the two sub-watersheds (Ploso and Kertosono) from the pre-period (1996–2006) to the post-period (2007–2017).