The Welang River in East Java, Indonesia, is a vital resource for the nearby communities providing water for daily use and supporting local agriculture. However, as cities expand and populations grow, the river has faced increasing problems such as flooding, erosion and pollution. In response, the Governments of Indonesia and the Netherlands, through its Partners for Water programme have initiated the Welang River Basin Transformation Project to tackle these challenges and protect both the river and the people who depend on it.

Nature-based solutions (NbS) are increasingly recognized as an essential strategy to address water and erosion challenges in watersheds. These solutions harness natural resources to tackle various water and soil issues. In areas where traditional infrastructure may be expensive, NbS offers a sustainable and cost-effective alternative that is easily replicable by local governments and communities.

In the upstream area of Welang Watershed, East Java, Indonesia, the NbS approach was applied through co-construction with the local community by employing a 3R methodology (retention, recharge, and reuse of water) through creation of simple gully plugs. These structures made from locally available materials like bamboo, stones and branches, serve to collect and temporarily store water during high rainfall flows, retain sediments and materials washed into the channel, and slow down small, concentrated flows.

Utilizing natural materials available in the area as gully plugs (left: bamboo, right: stone)

1. In Surorowo, the upstream area of Welang on the side of Mount Bromo, the project marked the communities’ first experience participating in an international project. Village officials played an important role in encouraging broad community participation. Two Focus Group Discussions involving various stakeholders were held to explain the value of the project and the interventions, to build trust and gain commitment of the community. Over two months of activities, at least 28 different gully plugs and gabions were installed on community land and initiated directly by the community.
2. The project location in Wonosari, the upstream area of Welang on the side of Mount Arjuno, is directly managed by the Wonosari Tea Plantation, making it easier to mobilize and cooperate with the workers. In just 12 working days, a total of 145 simple gully plugs made of stones, tree branches, and bamboo of various sizes were constructed.

Stakeholders involvement in demonstration activities

Institutional support
A Memorandum of Understanding (MoU) on sustainable water resources management in East Java was signed between the East Java Provincial Natural Resources and Public Works Agency (PUSDA), the government implementing agency of the project, and Perhutani, a state-owned enterprise managing the implementation site. This ensured stakeholder alignment and paved the way for replicating NbS across the province.

Monitoring and evaluation
Once implemented, effective monitoring becomes essential for tracking the progress of the installed structures and demonstrating their effectiveness. Field observations conducted by the State University of Malang assess the condition of the gully plug installations, their impact on sediment capture, erosion control, and soil stability. These insights help identify the most effective structure types, ensuring informed recommendations for future implementations.

The monitoring showed that series of gully plugs made sequentially following the channel from upstream to downstream are effective in retaining heavy water discharge and capturing sediment. On average, a 10-20 cm thick layer of sediment was found behind the installed gully plug structures, with the greatest accumulation of sediment occurring behind gully plugs with bamboo barricades filled with soil or grass and dense shrubs.
The other type of gully plug made of branches, was observed to have grown densely, providing a natural barrier to the heavy water discharge and sediment flowing along the channel.

Recommendation for replication
For replication, bamboo gully plugs and branch-made gully plugs are identified as the most effective, affordable, and easy-to-implement structures. These options are chosen based on their proven ability to capture sediment, ease of installation, support for vegetation growth, and the accessibility of materials, making them suitable for small-scale community implementation across diverse land uses.
On the other hand, gully plugs made from stone or even gabions tend to be more difficult for communities to implement without assistance from the government or third parties in procuring materials, but are structurally more robust and durable.

Miniseries on the Welang River Basin project

This is the second article in the miniseries on the Welang River Basin project, highlighting the role of youth in sustainable waste management. Below you can find the links to other articles in the series:

Article 1: The role of trusted advisors
Article 2: Practical implementation of Nature-Based Solutions
Article 3: Empowering youth for sustainable waste mangement
Article 4: A participatory design approach

Ask the oldest farmers in Nepal’s Bagmati province what the landscape once looked like, and the answer is always the same: greener, wetter, more alive. The Green Intelligence, a Dutch-Nepalese social enterprise supported by Partners for Water, is working to restore this landscape through productive agroforestry, a purpose-built mobile app, and an innovative blended finance model. Co-founder Matthijs van Rijn explains how a landscape approach is restoring fragile hillsides into resilient, income-generating forests.

In the mountains of Nepal’s Bagmati province, monoculture farming has left soils exposed and fragile. Monsoon rains are becoming increasingly intense and unpredictable, and when they fall, the water rushes downhill rather than soaking in. Wells dry up, and landslides destroy crops and homes. It was here, in 2021, that former engineer Van Rijn founded The Green Intelligence: a social enterprise implementing productive agroforests, including fruit, nuts and medicinal trees alongside existing crops, to improve both livelihoods and the landscape.

From village conversations to a landscape approach

“It all started with a few trees on a friend’s plot and plenty of conversations with local stakeholders,” shares van Rijn. “I drove around on my motorbike and asked the oldest people in villages what the landscape looked like before.” The conversations revealed that there used to be diverse, productive land, but also exposed the pressures that have taken over: less rainfall, ageing communities, and crops that deteriorate quickly and often don’t reach the market. Productive agroforestry emerged as the answer.

“Now, farmers are brought in through local stakeholder consultations at the municipality level,” says van Rijn. Those who sign up receive free training and trees – the costs are pre-financed by The Green Intelligence and recouped over time through carbon credits. The species are chosen in co-creation with Dutch and Nepali foresters and guided by what farmers themselves want to grow. “We look at what thrives at the various altitudes, what the farmer needs, and what can generate income,” Van Rijn explains.

An app built for the field

A purpose-built mobile app is what makes this approach work at scale. Farmers use it to register trees with geotagged photos, map their land by walking its perimeter, and access instructional videos on planting and tree care. “The app works offline and syncs automatically when connectivity is restored,” says van Rijn. “When a farmer uploads a photo of a healthy tree, our team reviews it remotely and releases a small financial reward – incentivising good care while generating verified data for carbon credit registration.” For farmers less familiar with smartphones, a community helper function was introduced, allowing a younger member to register trees on their behalf. “The platform now has 1,450 registered users and nearly 13,000 trees uploaded.”

A landscape-based approach

With support from Partners for Water, The Green Intelligence is now applying a landscape-based approach to catchment restoration, addressing degraded land not farm by farm, but at the scale of an entire municipality. “We work simultaneously on private agricultural plots and public land,” says van Rijn. The project brings together local governments, community forest user groups and farmers’ cooperatives in one shared effort. “Over the past year and a half, this has resulted in 250 hectares of agroforestry implemented and 250 hectares of community forest restored, impacting 7,200 community members.”

Connecting trees to international finance

“To make landscape restoration financially viable, we combine international carbon finance, local government contributions and development funding,” says van Rijn. Carbon credits are being developed under Gold Standard certification, a process requiring extensive documentation and independent verification. The app is essential here,” van Rijn adds. “Without the verified, geotagged data it collects, we cannot register carbon credits or provide transparency. It is what connects the trees to international climate finance and carbon markets.”

Dutch energy company Greenchoice is among the first international clients to commit to long-term climate finance for public land restoration at scale. “Their long-term commitment allows us to build trust and lasting relationships with local communities,” says van Rijn. “This is key to the success of the project”. Crucially, it also ensures the work initiated under the Partners for Water funding can continue and scale beyond the project period. Green Intelligence is currently exploring how to create market linkages for forest produce from the project sites.

When the community sees it works

The clearest sign of progress came from a single overgrazed hillside. After half a year of replanting and a grazing moratorium, grass returned. “Farmers had more fodder for their animals than they had seen in years and immediately asked if we could do the same on the next slope,” says van Rijn. But this is just a short-term example, he continues: “Ultimately, success is when communities generate a sustainable income from their land without chemicals, and when water levels and biodiversity are recovering. That will take thirty years.”
Meanwhile, The Green Intelligence is scaling the approach beyond Nepal. “Currently, we are also operational in Kenya, and in conversation with potential partners in Tanzania, Sierra Leone, Bhutan and Rwanda,” says van Rijn. “The same approach, adapted to each new context.”