Journal of Water Resources Planning and Management

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.

Dam failure can cause extraordinary flooding. Water and wastewater treatment plants, electricity generation facilities, bridges, highways, population centers, and other dams often lie downstream of a dam. If poorly maintained, aging dams can be overtopped by extreme rainfall events, and long-term loss of critical infrastructure services for many communities and regions may result. Such events are now more likely as the climate changes. How should we prioritize dams that need immediate attention and retrofit or remove them? Losses from a dam failure could exceed the infrastructure’s replacement costs, through cascading effects in multiple sectors such as electricity, transportation, water supply, and environmental services. The existing dam hazard classification frameworks in the US and many other countries do not formally characterize “hazard hotspots” considering these impacts. Given that there are over 90,000 dams at different stages of repair, maintenance, and budgetary constraints, a systematic approach is needed to rank their potential failure hazard and allocate resources for risk mitigation. In this paper, we synthesize an approach for preliminary ranking of the priority areas of concern. The approach is scalable over many regions for rapid assessment of magnitude and exposure of a dam failure. The estimation of the consequences of a dam failure, including its financial losses, as well as affected critical infrastructures and population, is explored using publicly available dam break and consequence tools as well as national infrastructure data sets.

Water managers must constantly balance investment in infrastructure upgrades to ensure reliable water supply with the affordability of water rates for consumers. As a result, trade-offs between water supply and financial objectives have become central to the long-term sustainability of utility operations. Few studies, however, have directly quantified decision-relevant financial benchmarks of water supply system adaptation. Benchmarks include debt covenants, guidelines required by creditors seeking assurance that debt will be repaid. Violation of covenant thresholds risks a downgrade of a utility’s credit rating, higher interest rates on future debt, and higher costs for new infrastructure. This work introduces an exploratory modeling framework that carefully couples adaptive water supply planning with financial modeling to better track how utility budgetary decision making can adapt to infrastructure expansion and future water demand growth. Demonstrated through an evaluation of infrastructure planning for Tampa Bay Water (TBW), results showcase TBW budgetary adaptation in response to water demand growth and supply expansion, quantifying the financial implications of infrastructure planning decisions and demand growth on water rates as well as the bond covenants. This study underscores the importance of integrating dynamic and adaptive financial modeling in providing realistic decision support that addresses both supply reliability and financial stability.

Abstract

From the Rocky Mountains in the US to the Sea of Cortez in Mexico, the Colorado River is one of the most managed and monitored rivers in the world. As decreasing river flows from drought and climate change continue to impact the Colorado River Basin, the US federal government, seven US states, and Mexico have signed agreements that would reduce deliveries, including a Drought Contingency Plan (DCP), an agreement among the US states and the Bureau of Reclamation, and Minute 323 (a treaty agreement between the US and Mexico). As part of the DCP, the US Bureau of Reclamation (Reclamation) committed to increasing conservation efforts to augment storage in Lake Mead. This paper presents an analysis of Reclamation’s Decree Accounting Reports that record water deliveries and conservation savings from 1964 to 2019. Overall, this analysis illustrates that (1) the agency has implemented significant conservation actions over the last three decades, (2) the agency has responded to increased accounting needs as dictated by national and international management agreements, (3) some actions have resulted in environmental costs, and (4) future actions could be designed to avoid environmental harms while also augmenting Lake Mead levels. As climate change continues to constrain Colorado River water supply, detailed accounting may help reveal areas for potential efficiencies or demonstrate where the greatest levels of savings have been reached while ensuring that environmental and social benefits are preserved.

Practical Applications

Over the last 100 years, humans have changed the path and personality of the Colorado River by distributing water to cities, communities, and agricultural fields to support over 40 million people. Throughout the twentieth century, the US federal government, seven US, and Mexico signed agreements enabling development of Colorado River water. By the early 21st century, as it became evident that water demands and climate change were reducing available supplies, these same governments signed agreements to reduce pressure on the river. All these agreements have, in part, been tracked by the US federal agency that manages the river, the Bureau of Reclamation (Reclamation), through Decree Accounting Reports. Since 1964, these reports have recorded how water is or is not accounted for that might be important to the future of the river. This paper examines those reports and reveals four main findings: (1) Reclamation has implemented numerous water conservation projects, (2) they have responded to new management agreements, (3) some of their actions have impacted the environment, and (4) there are proactive ways they can reduce environmental impacts and bolster water supplies in the future.

Abstract

In the US federal system, state governments play important roles between the federal and local levels in water resources planning, coordination, and regulation. How they coordinate these functions can indicate the degree of integration of their agencies and programs. A database of state programs was used to compile indicators of integration among water quality and quantity and drinking water source quality, as well as the status of comprehensive water planning. In most prior appropriation states and in some states in riparian areas, the management of water withdrawals and water quality remains in separate agencies. Some 35 of 50 states have a version of a “state water plan.” A scattered pattern of institutional arrangements shows that titles and functional coordination evolve in response to contextual situations, although state water management agencies have matured, and many have stable organizational forms. Water rights and regulatory controls for clean water and safe drinking water are firmly in place. Organizational structures are not likely to change much, but integration can be improved through management mechanisms and appropriate uses of planning, particularly at the watershed scale.

Practical Applications

State governments are pressed to be active in water resources management because they have authority in a geographic sphere closest to the scales of watersheds, river basins, and regional aquifers. This authority is important for states to respond to new threats like climate change, worsening floods, long-term drought, and public health challenges. Like in other levels of government, the workforce in state water management agencies is mobile and requires constant capacity building. Institutional memory is especially important, and state government executives require a rapid but comprehensive view of past experiences in organizational management in regulation, planning, and interactions with the federal and state governments. The paper provides a review of these experiences, along with suggested priorities for water management enhancements that may help in the future.

Abstract

This paper presents an innovative and comprehensive methodology considering yearly demand variability and environmental factors in the design of pumping stations serving closed water distribution systems. While a single daily pattern of demand is typically considered for the design in most cases in the literature, the new methodology considers a set of potential daily patterns of demand, each with its own probability of occurrence, both to obtain an accurate estimation of yearly operational costs and to guarantee the feasibility of the pumping station during the yearly demand peak. As an additional novelty of this work, environmental criteria, such as the impact in terms of greenhouse gas emissions, are considered in the design and combined with technical and economic criteria to rank various design alternatives based on the analytic hierarchy process (AHP). The methodology proves that it can yield cost-effective, technically sound, and environmentally friendly solutions in systems with various characteristics.

Practical Applications

The main contribution of this work is that it presents a standardized methodology for pumping station design in water distribution networks. An important advantage of this method is that it reduces the subjectivity of the designer and avoids assumptions during the design process by applying multicriteria decision analysis. This new method of pumping station design brings a different point of view to traditional design methods. While traditional design methods focus on minimizing project costs and operational costs, this new methodology considers technical, environmental, and economic aspects in a comprehensive manner during the design process. In addition, it considers demand variability in the design process, highlighting its effects and its importance in the case studies presented in this paper. In short, this methodology can be applied in any kind of pumping station design for real water distribution networks of different sizes. The results that this methodology yields demonstrate that pumping station solutions can be technically feasible and simple, economically profitable, and environmentally sound.

Abstract

This study presents a sustainability analysis of optimally designed water distribution networks (WDNs) under hydraulic failure situations using demand-driven analysis (DDA) and pressure-driven analysis (PDA). Two benchmark WDNs and their discrete designs are considered for this purpose. Hydraulic uncertain conditions are generated as a simultaneous variation of nodal demands and roughness coefficient using Monte Carlo simulation considering two different coefficient of variation (COV) values. The nodal performance of these networks is estimated using average nodal reliability (ANR) and average nodal vulnerability (ANV) metrics. The hydraulically efficient and critical nodes are ascertained from these measures, which are essential for proper operations and maintenance. Apart, the system performance measures, such as average system reliability (ASR), average system resilience (ASRes), and average system vulnerability (ASV), are evaluated. Since, all these performance measures resulted in different conclusions, an aggregate performance measure, the sustainability index (SI), is considered. Unlike other studies, the SI of WDN under uncertain scenarios and subsequently the average sustainability index (ASI) is measured. The evaluation of ASI that quantifies the network’s sustainability is intuitive and helps to select a better design from a set of optimal designs with similar costs and different diameter sets. Further, the study compares DDA and PDA analysis, demonstrating no-flow, full, and partial-flow situations. The statistical variation of the results is also illustrated. DDA underestimated the network hydraulics, which became faultier with the increase in uncertainty. The underestimation of hydraulic parameters misleads design, operational, and maintenance decision making. Thus, the study suggests PDA as the most reliable model for performance analysis and the optimal design of WDNs.

Practical Applications

The present study details the performance and sustainability analysis of optimally designed water distribution networks under hydraulic failure situations using demand-driven analysis and pressure-driven analysis. The hydraulic efficient nodes, critical nodes, and the best and least performing optimal designs, which are preliminary needs of any water supply policies, are determined. The hydraulic efficient nodes sustain the failure situations, whereas the critical nodes are key failure zones that need special attention during maintenance work. The sustainability index evaluated in the study will be helpful in clearly distinguishing the best designs from the given alternate options. The detailed comparison of demand-driven analysis and pressure-driven analysis in assessing the performance of water distribution networks under hydraulic uncertainties demonstrated that demand-driven analysis underestimates the water distribution network’s performance. Further, the performance assessment with demand-driven analysis became faultier with the increase in uncertainty. Consequently, the recovery cost for uninterrupted water supply policies would be overestimated using demand-driven analysis results. Thus, it is advisable to use pressure-driven analysis as an economical and reliable model for the design, performance, operation, repair, or maintenance works of water distribution networks.