Assessing the Remeneng River's Potential as a Sustainable Raw Water Source Using Water Balance and Pollution Index Approaches

Ardianta Selasa, September 08, 2026
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FORMOSA NEWS

Remeneng River Faces Seasonal Water Shortage Threat as Labuapi Population Surges

The Remeneng River in West Lombok Regency faces a structural risk of seasonal raw water deficits during dry seasons, driven by a growing local population expected to exceed 106,000 residents by 2035. This finding comes from a comprehensive study conducted by researchers Lalu Galeh Inggil Fatristya, Endah Wahyuningsih, and I Wayan Yasa from the Natural Resources and Environmental Management Master's Program at the University of Mataram, published in the International Journal of Contemporary Sciences in July 2026. The research highlights a critical vulnerability in the regional water infrastructure, as the Remeneng River serves as a primary raw water intake point for the regional water utility, Perusahaan Daerah Air Minum (PDAM) Giri Menang, to supply households across Labuapi District.

Growing Population Pressure on Peri-Urban Water Systems

Water demand in rapidly developing peri-urban zones like Labuapi District has escalated rapidly alongside housing expansion and a growing customer base. In tropical monsoon zones, surface water supply relies heavily on seasonal rainfall variations. Without a systematic assessment combining water supply quantities, reliable river discharge rates, and water quality metrics, the long-term sustainability of municipal drinking water services remains uncertain.

To address these challenges, the University of Mataram research team evaluated water availability using the F.J. Mock hydrological model, calibrated against historical daily discharge data from the Keru Automatic Water Level Recorder (AWLR) spanning 2010 through 2018. Water supply reliability was determined through a 90% dependable flow analysis ($Q_{90}$). Future population growth and raw water requirements for 2025 to 2035 were calculated using arithmetic projection methods. In addition, the team evaluated river water quality against Class I standards established under Indonesian Government Regulation No. 22 of 2021, using the Pollution Index (PI) method specified by the Decree of the Minister of Environment No. 115 of 2003.

Key Findings on Water Availability and Quality

The study revealed several critical insights regarding the hydrological dynamics and water quality of the Remeneng River:

  • Extreme Seasonal Discharge Fluctuations: The $Q_{90}$ dependable flow of the Remeneng River varies sharply across seasons, dropping from a peak of 1.144 $\text{m}^3/\text{second}$ in February (wet season) to a low of 0.009 $\text{m}^3/\text{second}$—fewer than 12 liters per second—in August (dry season).
  • Rising Water Demand: Labuapi's population is projected to increase from 84,959 in 2025 to 106,768 by 2035, driving raw water demand up from 143.30 liters per second in 2025 to 180.08 liters per second in 2035.
  • Inadequate Intake Capacity: The existing PDAM intake facility, designed with a capacity of 104 liters per second, is already insufficient to satisfy projected raw water demand starting in 2025.
  • Four-Month Water Deficit Period: Water balance calculations demonstrate that while water surpluses occur from November through June, severe water deficits emerge during four consecutive months, from July to October, when river flow cannot meet even existing intake capacity.
  • Seasonal Water Quality Variations: The river's water quality remains good during the dry season, with Pollution Index values between 0.534 and 0.880. Conversely, wet season runoff causes slight pollution levels, pushing the Pollution Index up to 1.513 due to elevated iron (Fe) concentrations and color turbidity carried by surface runoff and soil erosion.

Policy Implications and Real-World Impact

The findings provide crucial data for regional water resource planning and municipal infrastructure investment in West Lombok Regency. To prevent severe water shortages and ensure long-term public water access, the researchers recommend three key strategies: constructing small storage reservoirs or retention basins to capture wet season excess, implementing upstream watershed conservation to reduce erosion runoff, and improving distribution efficiency to minimize non-revenue water loss.

Highlighting the urgency of strategic intervention, the research team from the University of Mataram emphasized that integrated management is necessary to preserve municipal supply. "Harmonizing supply management through seasonal storage, upstream watershed protection, and strict loss control represents the most effective path toward securing sustainable drinking water services for Labuapi District," noted researchers Lalu Galeh Inggil Fatristya, Endah Wahyuningsih, and I Wayan Yasa.

Author Profiles

  1. Lalu Galeh Inggil Fatristya, S.T., M.Env.: Lead researcher and graduate of the Master's Program in Natural Resources and Environmental Management at the University of Mataram, specializing in water resource management and environmental hydrology.
  2. Dr. Ir. Endah Wahyuningsih, M.P.: Senior lecturer and researcher at the Postgraduate Program of the University of Mataram, with expertise in watershed management and environmental conservation.
  3. Prof. Dr. Eng. I Wayan Yasa, S.T., M.T.: Professor of Civil Engineering at the University of Mataram, specializing in water resources engineering, hydrological modeling, and drought analysis.

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