Rejoso watershed, at the foot of Mount Bromo in East Java, Indonesia, provides strategic ecosystem services, including the Umbulan Spring that lies downstream. In 2021, President Joko Widodo inaugurated a clean water system from the spring, which now supplies water to over 1.6 million people in the surrounding districts and the provincial capital of Surabaya.
In recent years, there has been more and more ecological pressure on the Rejoso watershed, both in the upstream and downstream areas. Land cover changes and stone and sand mining upstream and water drilling in the downstream areas for domestic, agricultural and for industrial purposes have put massive pressure on the water reserve.
A recent Montpellier University study assessing the recharge and functioning of the Bromo-Tengger aquifers estimated that in about 30 years the groundwater basin of the Rejoso watershed may dry up unless water use efficiency and water catchment conservation are implemented immediately. During the 1980s, water discharge from Umbulan Spring was up to 6,000 liters per second. Now, it is only half that amount and dropping.