Water-energy nexus in a desalination-based water sector: the impact of electricity load shedding programs

Seawater desalination is expanding rapidly as a response to global water scarcity and quality challenges, yet it is energy intensive, creating tight interdependencies between water and energy sectors. Prior work has largely focused on long-term or aggregate energy intensities across water production stages and sources, with fewer studies on short-term operational dynamics. This study addresses that gap by examining the short-term operational dependencies of desalination-based water supply on electricity availability and policy, focusing on Israel where desalination supplies over 80% of municipal demand and accounts for about 3% of national electricity use. The research questions are: how do desalination plants change production in response to electricity load shedding incentives during extreme events, and what are the implications for national water supply, regulation, and cross-sector oversight? Using high-resolution climatic, energy, and water data around a May 2019 heatwave and details of Israel’s ELSP, the study evaluates operational responses, system-level water balance impacts, and economic incentives, to inform joint energy–water management and policy design in desalination-reliant regions.

The water–energy nexus literature spans water use in energy production and energy use in water systems, with studies quantifying energy intensities across pumping, treatment, distribution, and by sector and source/technology (e.g., reverse osmosis vs. thermal processes). Many national/global assessments rely on databases from FAO, IEA, and EIA, while fewer works address short-term demand spikes and peak management. Desalination is recognized as energy-intensive with significant cost and environmental implications, and demand response tools (time-varying tariffs, ELSPs) are widely used for grid stability. Despite many integrated nexus frameworks and optimization approaches, practical implementation is hindered by institutional silos, misaligned incentives, and data-sharing barriers. This study builds on that literature by analyzing a real policy intervention (ELSP) at high temporal resolution, highlighting incentive misalignments during extreme conditions in a desalination-based system.

Data sources and types: The study compiled temporal climatic data (hourly temperature, humidity from the Israel Meteorological Service), hourly actual and forecasted national electricity demand (Electricity Authority), detailed ELSP rules and prices (Electricity Authority), daily water production from natural sources and reservoir storage (National Water Company, Mekorot), hourly desalinated water production by plant (Israeli Water Authority for Ashdod, Ashkelon, Hadera, Palmachim, Sorek), and organizational information on contracts and pricing (Ministry of Finance, consultant). Institutional insights were gathered via interview with the Head of Desalination Department at the Water Authority. Data were collated, cleaned, and temporally aligned. System-level analysis: Hourly weather, electricity demand, and desalination production were aligned to characterize responses during the May 21–26, 2019 heatwave. A daily mass balance for the Israeli National Water Supply System (INWSS) quantified changes in storage and contributions by source: ΔS_{t+1} = Q_GW,t + Q_SW,t + Q_DW,t − D_t, where Q_GW,t, Q_SW,t, Q_DW,t are daily groundwater, surface water, and desalinated production, and D_t total daily demand. Benefit–cost analysis: For a four-hour ELSP event, two scenarios were assessed (conservative, realistic) using plant flow rates (10,000–15,000 m³/h), energy intensities (3.0–3.3 kWh/m³), and ELSP compensation rates (up to $2/kWh; scenarios used $0.831/kWh and $1.662/kWh). The total nonproduction cost (CNPW) to a DP was computed as CNPW = ∑(SP + PR − EP×EI − AC)×Q_t over the event duration, with SP water selling price ($/m³), PR nonproduction penalty ($/m³), EP energy price ($/kWh), EI energy intensity (kWh/m³), AC auxiliary production cost ($/m³), and Q_t expected flow (m³/h). Benefits from electricity shedding were BELS = ∑ CR×E_i×Q_i, with CR the compensation rate ($/kWh). Assumptions included energy price $0.102/kWh, SP $0.693/m³, AC $0.139/m³, PR $0.2/m³, and consideration of a case where lost production is not fully compensated later. Currency conversion used 3.61 NIS/USD on May 23, 2019.

- Extreme event context: During May 22–24, 2019, a heatwave pushed peak electricity demand to 12 GW, exceeding forecasts by over 10%. Temperatures exceeded 40°C in many areas, humidity dropped to ~10%, and over 1,000 fires occurred within ~40 hours, elevating water service needs. - ELSP activation and plant response: The Electricity Authority activated ELSP on May 23–24, requesting four-hour reductions from large consumers including desalination plants (DPs). All five large DPs reduced output on May 23: three (Hadera, Palmachim, Ashdod) ceased production; one (Sorek) halved output on May 23 and stayed at full capacity on May 24; Ashkelon reduced despite not being formally enrolled. - Water system impacts: National water demand rose ~25% compared to the prior week. Mekorot utilized all available storage, surface, and groundwater sources to meet demand. Despite only a partial 4-hour curtailment, a noticeable multi-day decrease in desalination production was observed, stressing the INWSS and drawing down storage. - Economic incentives: For a typical 4-hour shedding event at 15,000 m³/h and 3.3 kWh/m³, energy shed ≈198,000 kWh; with $1.662/kWh compensation, income ≈$329,076. Under conservative assumptions (10,000 m³/h; 3.0 kWh/m³; $0.831/kWh), compensation ≈$99,720. - Nonproduction costs: Lost revenue at SP $0.693/m³, PR $0.2/m³, EP $0.102/kWh, EI 3.3 kWh/m³, AC $0.139/m³ yields total nonproduction cost ≈$25,020 (realistic) and $17,920 (conservative) for a 4-hour event. Net benefits to a DP ≈$304,056 (realistic) and $81,800 (conservative), i.e., shedding compensation is about 6–14 times nonproduction costs, creating strong incentives to curtail water production during ELSP. - Sectoral imbalance: The ELSP tariff structure favors electricity system needs but imposes short-term risks on water service reliability under extreme conditions. Institutional constraints prevented the Water Authority from compelling DPs to maintain production. - System statistics: Desalination in Israel supplies up to ~650 Mm³/y (~80% of municipal demand) with average energy intensity ~3.3 kWh/m³, accounting for ~3% of national electricity use (2019 total 72.5 TWh). National generation capability ~19.4 GW (2019), with limited real-time reserve during peaks.

Findings demonstrate significant short-term interdependencies and misaligned incentives between desalination-based water supply and electricity grid management. During an extreme heat event, ELSP-driven curtailments coincided with peak water demand and emergency needs (e.g., firefighting), forcing reliance on storage, groundwater, and surface water. The economic analysis reveals an agency problem: DPs maximize private benefits by participating in ELSP due to high compensation rates, while the water sector bears increased reliability risks and potential service degradation. This stems from institutional fragmentation—autonomous water and electricity regulators without mandated coordination or joint mechanisms to balance cross-sector objectives. Aligning incentives and governance is critical: conditioning DP participation in ELSP on water system status indicators, incorporating pre-agreed desalination production postponement incentives into contracts, and leveraging smart meters/grids for dynamic coordination could mitigate risks. While renewables and storage may reduce dependence on centralized power for desalination, large-scale integration remains challenging; nonetheless, it offers a long-term pathway to enhance resilience. Overall, integrated short-term operational planning—complementing long-term optimization—requires coordinated policies, robust data sharing, and decision-support tools to manage peaks and maintain water service levels.

The study shows that, in a desalination-dependent water sector, short-term electricity load shedding programs can create strong economic incentives for desalination plants to curtail production precisely when water demand peaks, jeopardizing service reliability. Using Israel’s May 2019 heatwave as a case, the analysis quantifies how ELSP compensation (up to ~6–14 times nonproduction costs) drives DP participation, leading to system-level stress requiring full use of storage and alternative sources. The main contributions are: (1) empirical, high-resolution evidence of short-term water–energy interdependencies under real policy action; (2) quantification of economic imbalances shaping DP behavior; and (3) identification of governance and data gaps limiting coordinated response. Policy implications include establishing joint water–energy management mechanisms, aligning tariffs and contracts with both private and sector-wide objectives, conditioning DP shedding on water system indicators, and improving data standards and sharing. Future research should test integrated short-term optimization frameworks across regions, evaluate contract/tariff designs that internalize cross-sector externalities, assess the role of distributed renewables and storage for large DPs, and develop real-time data architectures to support coordinated operations under extreme events.

- Case specificity: Results are based on a single extreme heatwave in Israel; generalizability may be limited across contexts with different market structures, resource mixes, and regulatory regimes. - Data access and standardization: Many datasets were obtained via requests; lack of standardized formats and centralized repositories, plus proprietary and sensitive data, may introduce gaps or uncertainties. - Assumption set in benefit–cost analysis: Economic scenarios assume specific tariffs, flows, costs, and a case where lost production is not fully compensated later. Actual DP operations may offset losses by increasing later production, altering net costs/benefits. - Attribution and lag effects: The observed multi-day desalination reduction relative to a 4-hour ELSP event suggests operational lags or constraints not fully captured by available data. - Renewable integration assessment: Discussion of renewables is qualitative for large-scale DPs; quantitative modeling of hybrid power systems was beyond scope. - Institutional insights: Stakeholder perspectives were limited to key informants; broader stakeholder engagement might reveal additional governance dynamics.