Groundwater-Extracting Rice Production in the Rejoso Watershed (Indonesia) Reducing Urban Water Availability: Characterisation and Intervention Priorities

Abstract

Production landscapes depend on, but also affect, ecosystem services. In the Rejoso watershed (East Java, Indonesia), uncontrolled groundwater use for paddies reduces flow of lowland pressure-driven artesian springs that supply drinking water to urban stakeholders. Analysis of the water balance suggested that the decline by about 30% in spring discharge in the past decades is attributed for 47 and 53%, respectively, to upland degradation and lowland groundwater abstraction. Consequently, current spring restoration efforts support upland agroforestry development while aiming to reduce lowland groundwater wasting. To clarify spatial and social targeting of lowland interventions five clusters (replicable patterns) of lowland paddy farming were distinguished from spatial data on, among other factors, reliance on river versus artesian wells delivering groundwater, use of crop rotation, rice yield, fertiliser rates and intensity of rodent control. A survey of farming households (461 respondents), complemented and verified through in-depth interviews and group discussions, identified opportunities for interventions and associated risks. Changes in artesian well design, allowing outflow control, can support water-saving, sustainable paddy cultivation methods. With rodents as a major yield-reducing factor, solutions likely depend on more synchronized planting calendars and thus on collective action for effectiveness at scale. Interventions based on this design are currently tested.

Mimicking nature to reduce agricultural impact on water cycles: A set of mimetrics

“…The Generic River Flow (GenRiver) Model (van Noordwijk et al, 2017b) is a distributed process-based model that transforms plot-level water balances to landscape scale. Beyond the estimates for water transmission, buffering peak flow and infiltration (W1 – W3A) of the current model version (https://www.worldagroforestry.org/output/genriver-generic-river-model-river-flow), an updated version (β-tested) has groundwater parameters to accommodate the functions W3B and W3C (Khasanah et al, 2021). Further steps link flow persistence F p and overland flow to slope/riparian stability (W5) and soil erosion/sedimentation (W6).…”

“…Groundwater over-use in lowlands is the main reason artesian spring discharge declines in the Rejoso watershed in Indonesia (Khasanah et al, 2021). Tree cover as a predictor of infiltration with thresholds differing between elevation zones on a single mountain (Suprayogo et al, 2020) leads to an optimal intermediate tree density phenomenon, similar to what was described for the Sahelian zone (Ilstedt et al, 2016; van Noordwijk et al, 2019).…”

Agroforestry-Based Ecosystem Services

“…Groundwater-extracting rice production in the Rejoso watershed (Indonesia) reducing urban water availability: characterization and intervention priorities [7] Rice production using ground-water from AF hillslopes…”

“…The tree canopy characteristics required for infiltration-friendly land use clearly varied over short distances with soil type and rainfall intensity showing that generic rules, such as a 30% forest cover requirement, cannot be the basis for local resource management using agroforestry concepts. A study of the water balance and the impacts of lowland water use in the same watershed through uncontrolled flow of Artesian wells found that equal attention is needed for the upstream and downstream parts of the watershed if urban water supply is to be secured [7].…”

Agroforestry-Based Ecosystem Services

“…Groundwater-extracting rice production in the Rejoso watershed (Indonesia) reducing urban water availability: characterization and intervention priorities [7] Rice production using ground-water from AF hillslopes Water balance effects of lowland water use…”