Affiliations: The Agency for the Assessment and Application
Technology (BPPT), BPPT Building 2, Floor 18, Jl. M.H. Thamrin 8, Jakarta
10340, Indonesia | Leibniz Center for Tropical Marine Ecology,
Fahrenheitstrasse 6, 28359 Bremen, Germany
Abstract: The Brantas River is the second largest river on the island of Java
which has undergone major changes in the past decades because of the demands of
an evergrowing population. Water management measures were mainly designed (i)
to provide flood protection, (ii) to provide raw water for irrigation,
households and industry, and (iii) to generate hydropower. The objective of
this paper is to delineate the history of development and attendant
environmental changes since 1970 as well as to address the effects of a mud
volcano eruption in 2006. Data from three gauging stations representing the
upstream, midstream and downstream portions of the Brantas River were chosen to
display patterns in discharge (1970-2003) and in nutrients (1991-1997). Overall
discharge decreased over time at all stations with the strongest decrease in
the downstream portion. The amplitude of seasonal changes in discharge was
highest in the downstream portion. Dissolved inorganic nutrient concentrations
increased slightly downstream as a result of land use. An eruption of a mud
volcano in 2006 added to the initially high sediment load of the river. A
portion of the mud was directed into the river leading to extremely high
suspended matter and low dissolved oxygen concentrations. As a large part of
the high suspended sediment load, already settled in the river, dredging was
initiated in order to avoid blocking of the river. The dredging material was
used for land reclamation. The high nutrient and sediment loads of the Brantas
River are to a large extent the result of intensive human activities in the
catchment like hydrological alterations and land-use change. Extreme natural
events like the mud volcano exacerbate the consequences of human alterations on
the water quality and biogeochemistry of the river.
Keywords: River, discharge, nutrient, mud volcano, land use change, Indonesia
