Dominated by mountainous topography, high rainfall, and erosion-sensitive soil types, and with the majority of its population living in rural areas as farmers, most of Indonesia’s watersheds are highly vulnerable to erosion. In 1984, the Government of Indonesia established 22 priority watersheds to be handled, which marked the start of formal soil and water conservation activities. Although it has not fully succeeded in improving watershed conditions from all aspects, something which is indicated by fluctuations in the area of degraded land, over the past 40 years the Indonesian government has systematically implemented various soil and water conservation techniques in various areas with the support of policies, laws and regulations, and research and development. These systematic efforts have shown positive results, with a 40% reduction in the area of degraded land over the last 15 years from 2004–2018. This paper reviews policy, implementation, and research and development of soil and water conservation activities in Indonesia over the last 40 years from the 1980s to 2020 and explores the dynamics of the activities.

Climate change is a major challenge for Indonesia due to its impact on food, water, energy sustainability, and environmental health. Almost all Indonesian regions are exposed to floods, landslides, soil erosion, drought, and heavy rains. In response to these challenges, the Government of Indonesia has determined integrated watershed management (IWM) to be one of the key programs to reduce greenhouse gas (GHG) emissions, as stated in the updated Indonesian nationally determined contribution (NDC). This paper intends to review Indonesia′s efforts in mitigating and adapting to climate change through an IWM approach, and its attempts to realize a decent life and environment for all communities. Improvement of the IWM can be conducted by strengthening the synergy between the responsible institutions for watershed management and the responsible institutions for handling mitigation and adaptation of climate change impacts. In addition, it is important to prioritize coordination, participation, and collaboration not only at the national government level but also at the international level, since numerous problems may exist in the transboundary between countries, and finding solutions should involve planning, implementation, monitoring, and evaluation. Implementing the micro watershed model (MWM), supported by culture, local wisdom, and traditional knowledge in communities, can be used to improve the current IWM.

In Indonesia, 2145 watersheds currently need to be restored, where around 21 million people spread over ± 23,000 villages live below the poverty line with a high dependence on forests. This condition requires an integrated approach in watershed management, which is aimed at technically restoring environmental conditions and ensuring the welfare of the people in it. One of the strategic approaches that can be taken is to revive local wisdom and traditional knowledge (TK), which has been eroded and neglected, and integrate them with technical approaches based on modern science and knowledge. Based on the author’s research and literature studies, this paper discusses the theoretical framework and implementation practices in integrating traditional knowledge into a science-based sociotechnical system to manage upstream watersheds sustainably. Based on the empirical evidence, efforts to create good biophysical and socio-economic watershed conditions can only be achieved through the active participation of farmers in adopting and integrating scientific technology into their traditional knowledge. This integration is realized in designing and implementing watershed management technology by considering the principles of suitability, applicability, feasibility, and acceptability. In the long term, it is necessary to document TK, patent it, and transfer it to the next generation to ensure that indigenous peoples’ and local communities’ social, cultural, and economic interests are protected.

Soil erosion and sedimentation are environmental problems faced by tropical countries. Many researches on soil erosion-sedimentation have been conducted with various results. Quantifying soil erosion-sedimentation and its temporal distribution are important for watershed management. Therefore, a study with the objective to quantify the amount of suspended sediment from catchments under various pine plantation areas was conducted. The research was undertaken during 2010 to 2017 in seven catchments with various percentage of pine coverage in Kebumen Regency, Central Java Province. The rainfall data were collected from two rainfall stations. A tide gauge was installed at the outlet of each catchment to monitor stream water level. The water samples for every stream water level increment were analyzed to obtain sediment concentration. The results showed that monthly suspended sediment of the catchments was high in January to April and October to December, and low in May to September. The annual suspended sediment fluctuated during the study period. Non-linear correlations were observed between suspended sediment and rainfall as well as suspended sediment and percentage pine areas. The line trend between suspended sediment and percentage of pine areas showed that the increase in pine areas decreased suspended sediment, with the slope of the graph is sharp at the percentage of pine areas from 8% to 40%, then is gentle for pine plantation areas more than 40%.

Jemelak Sub Watershed is close to the junction of two big rivers, i.e., Kapuas and Melawi. Therefore, this location faces environmental issues such as a flood. To avoid its possible damages, information on peak discharge becomes critical, particularly in calculating the drainage structure. This study was aimed to predict the peak discharge in this area using a rational method. The maximum daily rainfall data from 1998 to 2017 were divided into two periods of 10 years and analyzed. In the first period,  maximum rainfall rangesfrom98.6 to 176.3 mm, while the second period fluctuates from67.6 to 190 mm. Analysis of land cover described that 43.97% of secondary swamp forests turned into shrubs and swamp shrubs in the first period. Furthermore, about 800.71 ha of secondary swamp forest tuned into 582.80 ha of bare land, 181.04 ha of a plantation, and 36.88 ha of swamp shrubs in the second period. About 95.15% of shrubs were also turned into agricultural land mixed with shrubs in the second period. The result showed that the changes in the maximum daily rainfall and land cover simultaneously affected the improvement of the peak discharge by about 2.53% in the first period and 28.30% in the second period. If the peak discharge exceeds the river capacity, then the local flooding will occur along the river border. Keywords: land cover, peak discharge, rainfall, Jemelak