Drought Of Record Research Articles

Hands across the Water: How the 57-Year Dispute over the Edwards Aquifer Began, Persisted, and Was Resolved

The Edwards Aquifer is the primary source of water for a region in South-Central Texas that includes San Antonio and irrigated agriculture to the west. The aquifer also contributes to surface water flow in the Guadalupe River through Comal and San Marcos Springs, which are home to endangered aquatic species. In 1956, during the multiyear Texas drought of record, Comal Springs ceased to flow initiating a multi-decadal transboundary water dispute over the aquifer. This dispute pitted urban, agricultural, and environmental interests and surface water right holders against one another. In 1993, a federal district court ruled that the Endangered Species Act required that adequate flows from the springs be ensured for the endangered species. The Texas Legislature responded to the court by establishing the Edwards Aquifer Authority to regulate groundwater withdrawals. In 2007, with a key deadline looming to create a species protection plan, the Texas Legislature intervened again and mandated that the rival regional water interests engage in a stakeholder process to develop the plan. That process, which was called the Edwards Aquifer Recovery Implementation Program, resulted in a diverse group of parties with opposing interests collaborating to develop, approve, fund, and implement the landmark Edwards Aquifer Habitat Conservation Plan, which is in its 10th year of implementation.

Performance comparison of physical process-based and data-driven models: a case study on the Edwards Aquifer, USA

Physical process-based groundwater flow models are the major tools for studying fluid-flow behavior and for simulating the hydrological responses of water levels and spring discharge to human- and/or nature-induced triggers such as pumping and recharge. Such models are built with deep understanding of the physical processes and are based on geological models, developed by integrating data from geology, geophysics, and geochemistry. However, data-driven models can be built with limited data, eliminating the need for a detailed understanding of the physics. In this research, a data-driven model is built for simulating hydraulic responses (both groundwater levels and spring discharges) in a complex groundwater flow system of the Edwards Aquifer in Central Texas, USA, with the recurrent neural network (RNN) technique. The model is first trained and validated with the observation data of four targets—water levels from two index wells, and spring flow rates from San Marcos and Comal springs—from 2001 through 2015. The model is then used to predict the hydrological responses for the drought of record (1947–1958). The performance of the RNN model for the training, validation and prediction period is then quantitatively compared to that of the physical process-based MODFLOW model in terms of four statistical measures. The statistical measures suggest that the RNN model performs almost as well as the MODFLOW model. With further improvements, a data-driven model may be a surrogate to (or integrate with) a physical process-based model for simulating hydrological responses in the Edwards Aquifer.

Assessment of subsidence risk associated with aquifer storage and recovery in the Coastal Lowlands Aquifer System, Houston, Texas, USA

Abstract. In the Houston, Texas region, groundwater use is regulated by the Harris-Galveston Subsidence District (District) because of historical regional subsidence from groundwater development. The District regulates groundwater production in the Coastal Lowlands Aquifer System (CLAS) to mitigate subsidence through the implementation of District Groundwater Regulatory Plan. The District has successfully reduced groundwater pumping as a percent of demand regionally while controlling subsidence through the implementation of alternative water supplies. Aquifer Storage and Recovery (ASR) is an alternative water supply strategy that provides a means to store water underground and increase water supply more cost effectively than traditional storage expansion strategies. Groundwater users in the District are interested in the many potential benefits of ASR as a water supply strategy. Little is known about the potential effects on compaction and land surface subsidence resulting from ASR operations. Recognizing this, the District funded research on the potential subsidence risk associated with ASR. Two hypothetical, though representative, ASR projects were developed and analysed: (1) an industrial ASR project meant to provide water supply during a drought of record (DOR), and (2) a municipal ASR project designed to provide an annual municipal summer peaking water supply. Simulations of groundwater hydraulics and subsidence were performed at three potential locations within the CLAS to provide insight into variability associated with location and aquifer depth. Theoretical simulations confirmed the potential for subsidence associated with the application of ASR in the CLAS, although operating an ASR for summer peaking needs has less potential risk of subsidence than the DOR scenario in the scenarios simulated. The study simulations provide insight into how an ASR project may be designed and operated to minimize compaction and potential subsidence. Based on this study, ASR operated to address summer peaking showed the greatest potential to reduce additional compaction verses sourcing all water from groundwater. This theoretical study provides a basis for future research on subsidence associated with ASR and provides a framework for consideration for the regulation of ASR within the District.

An analysis of past and present megadrought impacts on a modern water resource system

ABSTRACTExtended drought is a concern for water resource sustainability in the Colorado River Basin of the western USA. Recent instrumental data are a limited rendering of drought risk, while paleoclimate data provide evidence of megadrought that could reoccur; but their impact analyses have not been reported to date. A 645-year tree-ring reconstruction of central Arizona, USA, streamflows reveals several threatening periods including a severe 16th-century multi-decade event. This study translated that record to net basin water supply with comparison to instrumental records to drive an operations model of a key resource system serving metropolitan Phoenix, Arizona. Cumulative system impacts and demand sensitivities find no system depletion to inoperable conditions for any drought of the past several centuries. The megadrought presently afflicting the region has become more severe than any in the paleoclimate record and should be considered the new drought of record for adaptation planning.

Climate-informed environmental inflows to revive a drying lake facing meteorological and anthropogenic droughts

The rapid shrinkage of Lake Urmia, one of the world’s largest saline lakes located in northwestern Iran, is a tragic wake-up call to revisit the principles of water resources management based on the socio-economic and environmental dimensions of sustainable development. The overarching goal of this paper is to set a framework for deriving dynamic, climate-informed environmental inflows for drying lakes considering both meteorological/climatic and anthropogenic conditions. We report on the compounding effects of meteorological drought and unsustainable water resource management that contributed to Lake Urmia’s contemporary environmental catastrophe. Using rich datasets of hydrologic attributes, water demands and withdrawals, as well as water management infrastructure (i.e. reservoir capacity and operating policies), we provide a quantitative assessment of the basin’s water resources, demonstrating that Lake Urmia reached a tipping point in the early 2000s. The lake level failed to rebound to its designated ecological threshold (1274 m above sea level) during a relatively normal hydro-period immediately after the drought of record (1998–2002). The collapse was caused by a marked overshoot of the basin’s hydrologic capacity due to growing anthropogenic drought in the face of extreme climatological stressors. We offer a dynamic environmental inflow plan for different climate conditions (dry, wet and near normal), combined with three representative water withdrawal scenarios. Assuming effective implementation of the proposed 40% reduction in the current water withdrawals, the required environmental inflows range from 2900 million cubic meters per year (mcm yr−1) during dry conditions to 5400 mcm yr−1 during wet periods with the average being 4100 mcm yr−1. Finally, for different environmental inflow scenarios, we estimate the expected recovery time for re-establishing the ecological level of Lake Urmia.

Estimation of Safe Yield of a Multipurpose Reservoir Using Weap: A Case Study of Thwake Reservoir, Makueni and Kitui Counties, Kenya

WEAP (Water Evaluation And Planning) is an integrated water resources planning model developed for more than 25 years by the Stockholm Environment Institute (SEI). In the WEAP model, dam and the water demands (upstream and downstream) are all schematized as an interconnected system ruled by allocation priorities (e.g., dam operation rules, priority for competing demands such as water supply, irrigation, hydropower, environmental flow, water storage in the reservoir). Thwake Reservoir is a multipurpose reservoir for hydropower generation, water supply and irrigation development in Kitui and Makueni Counties. The counties are well known as semi-arid hence the key objective of the study is to estimate the safe yield of the reservoir to enhance effective allocation of the water for different competing demands. Safe yield is based on projected future conditions that include a repeat of the most severe drought of record. Because the definition refers to projected future conditions, safe yield is inherently an estimated characteristic of future conditions that cannot currently be observed or measured. Thus any safe yield is only theoretically available at the time of the estimate. However, the reference to a repeat of the most severe drought of record indicates that past conditions are to be used to project future conditions. In this regard, 1000 years’ synthetic flows were generated using SWAT Model. In the model, 61 years (1952-2012) historical flows were used and the projected flows input into the WEAP model. The monthly reservoir balance for the base scenario and upstream dams development scenario were simulated. The performance of the Thwake Reservoir under different scenarios was assessed. Different sets of scenarios were explored for the Base Case and upstream development dams. These sets were tuned to the operational rules of the Thwake reservoir. Eventually, the dependable yield of the reservoir under different operating rules was estimated for both the base case and the upstream dam development scenarios. Thwake reservoir has an estimated dependable yield when it will be in operation before and after the development of the upstream dams.

Impacts of dam construction on streamflows during drought periods in the Upper Colorado River Basin, Texas

AbstractThe purpose of this study was to assess the impacts of dam construction on streamflow during a severe drought in the upper Colorado River basin (TX), upstream of Lake Buchanan reservoir. The region has experienced severe, prolonged droughts over the past century. To ameliorate the effects of drought, and increase water storage for use during dry periods, several dams were constructed on the mainstem and tributaries of the Colorado River upstream of Lake Buchanan since the late‐1940s. Analysis of flow at the gauge above Lake Buchanan indicated streamflow was significantly reduced during the recent drought (2009–2014), compared with streamflows during the ‘drought of record’ (1950–1957). The construction of these upstream dams reduced streamflow by intercepting and storing water. It is concluded that building reservoirs in the western portion of the basin, largely in response to past droughts, although increasing water supplies for local uses, exacerbated the downstream effects of the hydrological drought, essentially making it the worst in recorded history.

The El Niño That Finally Was and the Drought That Finally Ended

ABSTRACTThe second worst drought in Texas history began in 2011 and ended abruptly in the spring of 2015 with exceptionally heavy rains linked to an El Niño event in the Pacific. The drought was exceeded only by the drought of record in the early 1950s that also ended with a strong El Niño in the spring of 1957. This begs the question of what is the history of drought termination in Texas by El Niño events? In reviewing the Texas drought record since 1950, half the droughts did end with increased rainfall during winter into spring El Niño events.

Is climate change implicated in the 2013–2014 California drought? A hydrologic perspective

AbstractCalifornia has experienced severe drought in 2012–2014 (which appears to be continuing into 2015), with especially low winter precipitation and mountain snowpack in winter 2013–2014. However, the extent to which climate change is implicated in the drought, if at all, is not clear. By applying modeling and statistical approaches, we construct a historical record of California snowpack, runoff, and other hydrological variables of almost 100 years in length and use the reconstructed records to analyze climate trends in the Sierra Nevada and their impact on extreme drought events in the historic record. We confirm a general warming trend and associated decreasing trends in spring snowpack and runoff. We find that the warming may have slightly exacerbated some extreme events (including the 2013–2014 drought and the 1976–1977 drought of record), but the effect is modest; instead, these drought events are mainly the result of variability in precipitation.

Comparison of the Recent Drought in Texas to the Drought of Record Using Reanalysis Modeling

The current drought in Texas has become the second worst in the last 120 years, exceeded only by the 1950s drought of record. It is easy to compare the two in terms of area, length, and severity using the Palmer Drought Severity Index (PDSI), and the underlying atmospheric process can be reconstructed with data from the National Oceanic and Atmospheric Administration (NOAA) reanalysis model. Reanalysis is a comprehensive, global data set produced by the National Centers for Environmental Prediction. The historical surface observations, balloon soundings, and satellite data have been reprocessed or reanalyzed with a sophisticated computer model. Thus, it is possible to compare the 1950s drought and the current drought directly using data from the same model. The meteorological processes operating in these droughts showed similar patterns of 500 mb pressure, outgoing longwave radiation, and geopotential height.

New York City Panel on Climate Change 2015 Report. Chapter 1: Climate observations and projections.

Radley Horton,1,a Daniel Bader,1,a Yochanan Kushnir,2 Christopher Little,3 Reginald Blake,4 and Cynthia Rosenzweig5 1Columbia University Center for Climate Systems Research, New York, NY. 2Ocean and Climate Physics Department, Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY. 3Atmospheric and Environmental Research, Lexington, MA. 4Physics Department, New York City College of Technology, CUNY, Brooklyn, NY. 5Climate Impacts Group, NASA Goddard Institute for Space Studies; Center for Climate Systems Research, Columbia University Earth Institute, New York, NY

Applying multi‐parameter runoff elasticity to assess water availability in a changing climate: an example from Texas, USA

AbstractAdaptation and mitigation efforts related to global trends in climate and water scarcity must often be implemented at the local, single‐catchment scale. A key requirement is understanding the impact of local climate and watershed characteristics coupled with these regional trends. For surface water, determination of multi‐parameter runoff elasticities is a promising tool for achieving such understanding, as explored here for two surface‐water dependent basins in Texas. The first basin is the water supply for Dallas‐Ft. Worth (DFW), and exhibits relatively high precipitation elasticity (proportional change in runoff to change in precipitation) εP = 2.64, and temperature elasticity εT = − 0.41. Standard precipitation–temperature elasticity diagrams exhibit unusual concave contours of runoff change, indicating influence of additional parameters, which can be isolated using multi‐parameter approaches. The most influential local parameter in DFW is unexpected reduced runoff fraction in cooler wetter years. Those years exhibit increased summer (JJA) precipitation fraction, but predominant cracking soils in DFW minimize JJA runoff, yielding negative . A comparative basin near Houston shows positive , reflecting the local impact of tropical cyclones and lesser abundance of cracking soils. Both basins exhibit positive elasticity to 1‐year previous precipitation (e.g. DFW εP − 1 = 1.24), reflecting the influence of soil moisture storage. Only DFW exhibits negative elasticity to 2‐year previous precipitation (εP − 2 = − 0.65), reflecting multi‐year influence of vegetation growth and increased evapotranspiration.Using these elasticities, analysis of historical multi‐decadal climate departures for DFW indicates the 80% decrease in runoff during the 1950–1957 drought of record was primarily caused by reduced precipitation. Runoff 56% above‐normal during an unprecedented 1986–1998 wet period was primarily caused by increased precipitation. Since 2000, despite precipitation slightly above normal, runoff has decreased 20%, primarily in response to ∼ 1∘C warming. Future precipitation droughts superimposed on this new drier normal are likely to be much more severe than historical experience would indicate. Copyright © 2014 John Wiley & Sons, Ltd.

Decrease in southeastern Australian water availability linked to ongoing Hadley cell expansion

AbstractSoutheastern Australia experienced the worst drought of the instrumental record from 1997 to 2009, which was broken by Australia's wettest 2 year period on record (2010/2011). This drought was primarily a cool season (April to October) phenomenon. In contrast, the breaking of the drought was a warm season (November to March) phenomenon. This reduction in winter rainfall along with an absence of very wet months led to a greater reduction in streamflow across the region than would be anticipated based on the 12% reduction in mean annual rainfall alone. The results presented in this article have linked the extent, duration, and severity of this drought to the ongoing observed expansion of the Southern Hemisphere Hadley cell at a rate of 0.5°/decade. This expansion has intensified the subtropical ridge over southern Australia, pushing cool season midlatitude storm tracks further south, leading to a reduction in winter rainfall and runoff across the region.

Paying for Water: The 83rd Legislative Session and the $2 Billion Water Infrastructure Bank

The current drought has been hanging over Texas for three years. Meteorologists have predicted that it could last for another five years and could become worse than the infamous 1950s drought of record, which “reshaped Texas, ruining thousands of farmers and ranchers and pushing rural residents to migrate out of the country and into the cities.”Among Texas leaders, there is a general consensus that the state must act now to ensure its longterm water security, and as the legislature convened for its 2013 session, many observers predicted water would emerge as a marquee issue. And it did, with lawmakers introducing numerous water-related bills.Three of these bills are aimed at financing enough water infrastructure projects to assure longterm water supplies for the state: H.B. 4, H.B. 1025 and S.J.R. 1. These bills could have a profound and long-lasting impact on Texas water law and water resources. H.B. 4 revamps the agency that provides state financing for water infrastructure, the Texas Water Development Board (TWDB). Together with H.B. 1025 and S.J.R. 1, it creates two new funds to be used by TWDB, contingent upon voters Texas approving Proposition 6 (as authorized by S.J.R. 1) in the November 5 special election.The new funds are the State Water Implementation Fund for Texas (SWIFT) and the State Water Implementation Revenue Fund for Texas (SWIRFT). If Proposition 6 passes, SWIFT will receive a $2 billion appropriation from the Economic Stabilization Fund (“Rainy Day Fund”). TWDB may disburse money from SWIFT through a “bond enhancement agreement” to certain other TWDB funds, which may then provide approved forms of financial assistance to applicants for state aid. Sister fund SWIRFT provides TWDB with new revenue bonding authority and provides an additional mechanism for distributing SWIFT money.While H.B. 4 sets broad parameters for SWIFT and SWIRFT, it delegates significant responsibility for creating, designing and operating those funds to TWDB. Many of the questions that a politically high-profile and financially high-dollar bill such as H.B. 4 raises – which projects will benefit, how exactly will the money be used, and how long will the money last – will remain unanswered until TWDB promulgates regulations to implement its statutory commands.In anticipation of the November 5 special election, and of the extensive rulemaking processes that will follow if Proposition 6 succeeds, the Center for Global Energy, International Arbitration and Environmental Law has prepared this white paper. It explains the key provisions in H.B. 4 and Proposition 6. It explores the contours and inflection points in complex legislation that – aside from a salient few details – remains relatively unfamiliar to the general public and even to those who work regularly on water policy issues.

Low-Flow Variations in Source Water Supply for the Occoquan Reservoir System Based on a 100-Year Climate Forecast

AbstractThe onset of climate and land-use change is forcing water managers to develop new techniques in response to the changing environment. This study uses established techniques to incorporate both projected climate change and projected land-use change into a hydrologic model of the Occoquan watershed, which encompasses an area of approximately 1,550 km2 in northern Virginia. The techniques used develop a future projection of weather that recreates the historic time series, including the drought of record, as influenced by climate change, thereby facilitating integration into existing water-management practices. Incorporating land use and using multiple metrics for analysis of low flow (drought) allows for the determination of variations between the historic and future model flows. This study revealed a likelihood of increased low-flow volumes for the Occoquan watershed from both climate and land-use change, the majority of which were produced from land-use change in combination with expanded reclaime...

100 Years of benthic foraminiferal history on the inner Texas shelf inferred from fauna and stable isotopes: Preliminary results from two cores

Coastal regions, such as the Texas–Louisiana shelf, are subject to seasonal hypoxia that strongly depends on the magnitude of freshwater discharge from local and regional river systems. We have determined benthic foraminiferal fauna and isotopic compositions in two 210Pb dated box cores (BR4 and BR5) to examine the evidence for nearshore hypoxia and freshwater discharge on the Texas shelf during the last 100 years. The 210Pb chronologies of both cores reveal sedimentation rates of 0.2 and 0.1cmyr−1, translating to ∼60 and ∼90 year records. The fauna of both cores were almost exclusively composed of Ammonia parkinsoniana and Elphidium excavatum, indicating euryhaline ambient waters. The Ammonia–Elphidium (A–E) index, a qualitative measure of low oxygen conditions, shows an increase from values between 20 and 50 to near 100 in both cores, suggesting low oxygen conditions between 1960 and the core top. Between 1950 and 1960 (9–10cm), low A–E values in BR4 coincide with high δ18O and δ13C values greater than 0‰ and −1‰ respectively. This event corresponds to severe drought (the Texas Drought of Record) over the Brazos River drainage basin and considerably reduced river discharge from 1948 to 1957. High A–E values prior to this event imply low-oxygen conditions were prevalent prior to anthropogenic exacerbation of Louisiana shelf hypoxia and at least since the dredging of a new Brazos River delta in 1929. Elphidium excavatum δ13C values are very low (−4‰) and indicative of significant vital effect. The δ13C values of A. parkinsoniana average −3‰ and exhibit little variability, most likely reflecting pore waters influenced by aerobic and anaerobic respiration. The association of lowered Brazos River discharge with more oxygenated shelf bottom waters suggests Brazos River discharge and shelf hypoxia are linked, but the influence of Mississippi–Atchafalaya discharge can also contribute to shelf stratification.

Upland contribution of sediment and runoff during extreme drought: A study of the 1947–1956 drought in the Blackland Prairie, Texas

summary The 1950s drought severely impacted a 1.1 million km 2 area in the central US. This drought, along with the famous 1930s drought, was among the most severe of the 20th century for large areas and is the drought of record for water supply planning in Texas. At the USDA-ARS Riesel Watersheds during the drought, average annual rainfall was reduced 27%, which produced 75% less runoff and 35% less sediment yield. Rainfall intensity during the drought was, however, typically greater than for the non-drought period. Based on long-term data from the Riesel Watersheds, the mean, 75th, 90th, and 95th percentile values of sediment yields on days with measureable soil loss were larger for the drought than non-drought periods. These results reflect the increase in rainfall intensity during the drought but more importantly the increased efficiency of drought rainfall to dislodge and transport sediment, which is attributed to the combined effects of reduced vegetative cover and increased soil erodibility. The potential for high sediment yields during drought periods illustrates the need to consider this landscape vulnerability in long-term planning and assessment and the importance of long-term monitoring to predict water supply impacts. This is especially evident in Texas, which is expected to experience a dramatic increase in population and water demand this century, with a corresponding decrease in reservoir storage capacity due to sedimentation.

Long‐term changes in flow regime and fish assemblage composition in the guadalupe and san marcos rivers of texas

AbstractRiverine flow regimes are naturally dynamic, but become increasingly homogenized following anthropogenic flow alteration. Loss of dynamism disrupts naturally occurring structuring mechanisms within the associated biotic communities, at times causing shifts in composition. Here we considered how stream fish assemblages in two Central Texas rivers changed after alteration of flow regime by either construction of a mainstem, deep storage reservoir or flood‐retaining structures. Following impoundment, number of large and small floods increased from 0.81 to 1.07 floods per year (FPY) in the upper Guadalupe River, decreased from 0.84 to 0.42 FPY in the lower Guadalupe River and decreased from 0.87 to 0.7 FPY in the San Marcos River. Historical ichthyofauna data ranging from 1938 to 2006 were used to assess changes in assemblage composition and species abundance. Assemblages did not differ in the upper Guadalupe River (Bray–Curtis index = 37.4%; ANOSIM global R = 0.079, p = 0.08), but did differ in the lower Guadalupe River (25%; global R = 0.409, p < 0.01) and San Marcos River (27%; global R = 0.19, p < 0.01). In general, habitat generalist species dominated assemblages during periods of reduced flood frequencies (i.e. drought of record; following impoundment), whereas regionally endemic species (N = 3) and substrate and broadcast spawning species (N = 5) declined (b1 < 0; α = 0.05). Based on the results from this study, managing flows in the lower Guadalupe River to mimic historical timing of flood pulses might attenuate contemporary disruption of natural assemblage composition. Copyright © 2010 John Wiley & Sons, Ltd.

Climate Change Impacts on Texas Water: A White Paper Assessment of the Past, Present and Future and Recommendations for Action

Texas comprises the eastern portion of the Southwest region, where the convergence of climatological and geopolitical forces has the potential to put extreme stress on water resources. Geologic records indicate that Texas experienced large climate changes on millennial time scales in the past, and over the last thousand years, tree-ring records indicate that there were significant periods of drought in Texas. These droughts were of longer duration than the 1950s “drought of record” that is commonly used in planning, and they occurred independently of human-induced global climate change. Although there has been a negligible net temperature increase in Texas over the past century, temperatures have increased more significantly over the past three decades. Under essentially all climate model projections, Texas is susceptible to significant climate change in the future. Most projections for the 21st century show that with increasing atmospheric greenhouse gas concentrations, there will be an increase in temperatures across Texas and a shift to a more arid average climate. Studies agree that Texas will likely become significantly warmer and drier, yet the magnitude, timing, and regional distribution of these changes are uncertain. There is a large uncertainty in the projected changes in precipitation for Texas for the 21st century. In contrast, the more robust projected increase in temperature with its effect on evaporation, which is a dominant component in the region’s hydrologic cycle, is consistent with model projections of frequent and extended droughts throughout the state. For these reasons, we recommend that Texas invest resources to investigate and anticipate the impacts of climate change on Texas’ water resources, with the goal of providing data to inform resource planning. This investment should support development of 1) research programs that provide policy-relevant science; 2) education programs to engage future researchers and policy-makers; and 3) connections between policy-makers, scientists, water resource managers, and other stakeholders. It is proposed that these goals may be achieved through the establishment of a Texas Climate Consortium, consisting of representatives from academia, industry, government agencies, water authorities, and other stakeholders. The mission of this consortium would be to develop the capacity to provide decision makers with the information needed to develop adaptation strategies in the face of future climate change and uncertainty. Citation: Banner JL, Jackson CS, Yang ZL, Hayhoe K, Woodhouse C, Gulden L, Jacobs K, North G, Leung R, Washington W, Jiang X, Casteel R. 2010. Climate Change Impacts on Texas Water: A white paper assessment of the past, present and future and recommendations for action. Texas Water Journal. 1(1):1-19. Available from: https://doi.org/10.21423/twj.v1i1.1043.

Water resources planning and management at the Salt River Project, Arizona, USA

The Salt River Project (SRP) was created in the early 1900s to assure an adequate water supply for its shareholders in the Salt River Valley, Arizona, USA. The straight forward job of storing inflows and meeting demand from a single reservoir system soon became more complex. As the population of the Salt River Valley swelled, additional reservoirs were added to the system, alternative supplies of water were developed, and hydro-power generation became a financial consideration in reservoir operations. Nevertheless, the primary operational objective continues to be the conjunctive management of multiple sources of water to ensure an adequate carry-over supply of water for SRP’s shareholders in the Salt River Valley. This objective has traditionally been accomplished by managing the reservoir system as if each time the reservoirs fill to capacity is the beginning of an extended drought comparable to the worst historical drought in recorded history. Over the past 20 years, several subtle yet significant events have taken place which raise concerns regarding SRP’s traditional method of water planning and management. Changes in demand patterns as land is converted from mainly agricultural use to urban use, an ongoing drought rivaling the historical drought of record, tree-ring studies suggesting even more severe droughts having occurred in pre-historic times and, the specter of a changing climate due to global warming all suggest that a business as usual approach to water management and planning may no longer be appropriate.