“Reliable water supply” does not have a clear definition in the Western United States, where water resources are limited and such a definition would be especially useful. In Utah, the three water agencies and 500 public water systems have no consistent method to define, evaluate, and report it, potentially leading to an inability to meet regulatory water demands. We propose a unified definition of reliable water supply for Utah’s public water suppliers that can also be used elsewhere. The qualitative definition we propose is necessary to precede quantitative evaluations, set policy, and provide consistency to water resources management. We derive our definition from a two-part qualitative analysis: 1) an extensive review of existing definitions in industry and academia and 2) semi-structured interviews with managers of six diverse Utah water utilities. We propose that water supply be defined by three overlapping components—hydrology, infrastructure, and governance—and that reliability be defined by the capacity of the limiting component.

Great Salt Lake has receded in recent years. Among many options proposed to augment inflows is a pipeline from the Pacific Ocean. To inform discussion, we estimate a lower bound for the ongoing energy requirements, assuming one-third of the recommended additional inflow will be pumped through a single, smooth, large-diameter diameter pipeline along a fictitious, shortest route without mountains. Accordingly, pumping would require at least 400 megawatts of electricity during operation, an amount equivalent to a large power plant, or 11% of Utah’s annual electricity demand. Given current energy prices and fuel mixes, the electricity would cost over $300,000,000 annually and emit nearly 1,000,000 metric tons of carbon dioxide annually, equivalent to 200,000 passenger vehicles. The figures could easily triple with longer routes, mountainous terrain, higher flows, smaller diameters, multiple pipelines, less-efficient pumps, and any required treatment. We present this estimate trusting that feasibility studies will include complete details.

While most rivers and lakes follow predictable principles of hydrology and geology, a few defy the rules. Some rivers diverge rather than converge; some rivers flow two directions; some lakes have not one but two outlets; some watersheds have ambiguous boundaries. The scientific literature on these exceptions is sparse, scattered, and, in some cases, conflicting. We provide an authoritative overview of nine unusual natural drainages in North and South America, including river bifurcations and bifurcation lakes: Casiquiare River, Arroyo Partido, Wayambo River, Atchafalaya River, North Two Ocean Creek, Divide Creek, Committee’s Punch Bowl, Echimamish River, and Wollaston Lake. Most instances are found on flatlands and saddles. Some watershed boundaries are still unresolved or even dynamic, suggesting river formation in progress. We discuss the exploration, geophysical settings, hydrology, ecology, use, and management of these extraordinary drainages.

Following wildfires, riverine water quality in forested watersheds is prone to degradation, impacting drinking water treatment and potentially causing increased emissions because of additional electricity consumption. We explore the potential for climate-based financing to support wildfire mitigation and watershed restoration and thereby reduce potential water treatment energy demand within the Provo River watershed of Utah, USA. Pre-and post-wildfire erosion and water quality in the Provo River is modeled using GeoWEPP. Energy data from the Don A. Christiansen Regional Water Treatment Plant in the watershed and related literature data are used to estimate the increase in energy use for treating degraded water. We find that most watershed areas are not subject to large treatment demand changes, but a few hotspots are prone to increased sediment. In the Provo River watershed, on average, a fire in a single 12-digit hydrologic unit code sub-watershed corresponds to an additional 350 metric tonnes of carbondioxide-equivalent emissions for one year following a wildfire event due to increased energy by the water treatment plant. If wildfire risk is reduced, the avoided emissions can generate a potential of $88,500 annually in carbon credit revenue (at $10/CO2e credit) for the HUC8 subbasin contributing to water treatment. Synopsis This study demonstrates a method for modeling pre-and post-fire erosion and connects the impacts to energy use and emissions associated with a downstream drinking water treatment plant.

Agricultural irrigation is the largest consumer of water in the United States. Many changes have occurred over the years, but we question the recent attention on efficiency. Comparing 2015 and 1985, we find that more land is being irrigated with less water: irrigation withdrawals fell by 14%, irrigated area expanded by 11%, and flood irrigation was substantially displaced by sprinkler and microirrigation systems. However, consumptive water use fell by only 1%, and return flows-an important part of the water balance that supports many downstream needsdeclined by 39%. This gain in efficiency and loss in return flow, without any apparent saving of water, is the conflicting legacy of U.S. irrigation. We propose the links among irrigation efficiency, return flows, and consumptive water use as a central theme around which to organize future irrigation research, policy, and management. We call on state and federal agencies that fund research and adoption of improved irrigation practices to require accounting of all aspects of the water balance-including return flow-and promote sustainable, basin-scale water conservation.

Water utilities today need to reinvigorate aging infrastructure, finance capital improvements, and reduce energy use. Self-funding-using internal funds to invest in capital projects that save energy, and then pay back the investment with the savings-is a strategy that hits all three needs. An ideal self-funded project is one where other funding is insufficient, an internal loan is available, the project is permanent, and savings are ongoing. An example is discussed. Concepts Water professionals have identified aging infrastructure and capital financing as two of the top three challenges facing the water industry (AWWA 2023). At the same time, water utilities are motivated to reduce their energy use, whether to save money, meet climate goals, or adjust to an evolving electricity market (Sowby et al. 2023; Patel et al. 2022). But investing in energy-efficiency projects can be expensive, even if the payback is obvious.

Even though drinking water utilities are not meant to fight wildfires, they quickly become stakeholders, if not first responders, when their resources are needed for firefighting. The August 2023 wildfires on the island of Maui, Hawaii, USA, have highlighted weaknesses at this intersection. We analyze this extreme case to support disaster-response lessons for water utilities and to guide further research and policy. First, emergency water releases were not available in a timely manner. Second, fire and wind toppled power lines, causing power outages that inhibited pumping water. Third, many structures were a total loss despite water doused on them, consuming valuable water. Finally, water was lost through damaged premise plumbing in burned structures, further reducing system pressure. These conditions emphasize that water utilities need to access emergency water supplies quickly, establish reliable backup electricity, coordinate with firefighters on priority water uses, and shut valves in burned areas to preserve water. While further research will certainly follow, we present these early lessons as starting points.

The original article proposed a sampling method for detecting continuous contamination sources, a method that does not require elaborate water quality data or real-time sensors. The method has practical merit for many water utilities but the authors' work has some limitations not discussed in the article that we comment on here. First, the authors use terms like "real-world system" to refer to a study done with a model, which may mislead readers. Second, the method is advertised as simple but actually requires some advanced tools and steps that are not fully described and that may not be available to practitioners. Third, determination of flow directions is not always explicit and usually requires a hydraulic model, which the authors happened to have, but may not be available for every system. Fourth, the authors do not adequately describe the hydraulic model; their figures show networks that differ from the provided models and may have differing lengths or flow directions that affect the analysis. Finally, the study data are not provided as per the Data Availability Statement, but doing so could help overcome these limitations and make the method more useful.

Energy intensity—an expression normalizing pump energy use by water volume, also called specific energy—is becoming a more commonly used key performance indicator as water utilities seek to analyze and optimize their energy use. Its theoretical basis, however, has not been well documented. Beginning with Newton's second law, we derive the pump power equation and the pump energy intensity equation, provide specific values for engineering reference, and discuss applications. In a perfectly efficient system pumping water, the minimum energy intensity is 0.00272 kWh/m3 per meter of head or 3.14 kWh/Mgal per foot of head. Considering typical pump efficiencies, these references may be scaled and used for analyzing pump performance or estimating future energy uses. As a key performance indicator, energy intensity is a convenient input-output quotient where both parts can be observed directly, enabling tracking over time and comparison among individual facilities. As a planning tool, energy intensity can estimate expected energy use without having to know details of the pumping system. Such are the high-level applications water systems may find as a prelude to deeper energy analyses in pursuit of sustainable infrastructure.

Fluid mechanics is a field rife with diverse units of measure and, consequently, potential for errors. Unlike their experience in mathematics, undergraduate students must learn to manipulate both numbers and units in order to satisfy dimensional homogeneity and succeed in engineering. Using written exam responses from students in an undergraduate fluid mechanics class, this paper 1) compares scores according to whether students carefully handled units or not and 2) provides examples of mistakes that may have been avoided by analyzing units. In the exams, students who consistently tracked units scored higher and with less variance than those who did not; both results are statistically significant. The selected examples highlight errors in algebra, fluid properties, and geometry that may have been detected had students properly handled units. The findings suggest that the habit of analyzing units is desirable for students to develop, helping them both understand concepts and check their work as they become engineers.

Hydraulic modeling is the backbone of water system engineering. Understanding “the 3 A’s of hydraulic modeling”—Accuracy, Applicability, and Accessibility—will help you get the most out this important tool.Archived from The Flow, Winter 2021 (Intermountain Section, American Water Works Association)

This study examines water demand in 19 public water systems in Salt Lake County, Utah, USA, including the metropolitan and economic center Salt Lake City, as water users adjusted to sudden shifts in work and social activities due to the COVID-19 pandemic. We develop water demand models based on climate and population during a pre-COVID period and evaluate whether these models hold for the initial pandemic year 2020 and beyond (2021) by comparing predicted and observed water demands. Our analysis captures a shift in water demand away from Salt Lake City into surrounding communities and from non-residential to residential settings. During 2020, total countywide water demand rose by 8.5% overall. In Salt Lake City, residential water demand rose by 5.3% while non-residential water demand fell by 4.9%; in the rest of the county, residential water demand rose by 14.5% while non-residential water demand rose by 2.9%. We attribute the redistribution of water demand to stay-at-home activity during much of 2020. The observed post-pandemic shifts demonstrate how water demands can quickly and substantially deviate from historic conditions. Additionally, poor model performance for demands in 2021 indicate that the temporary but major disruption of the pandemic may have resulted in a more sustained, long-term shift in water demands. Municipal water systems may benefit from planning scenarios that consider the scale (magnitude and persistence) of corresponding impacts on hydraulics, water quality, and revenue.