Sarah E. Null

Utah State University | USU · Department of Watershed Sciences

Water management usually considers both economic and ecological objectives, and involves tradeoffs, conflicts, compromise, and cooperation among objectives. Pareto optimality often is championed in water management, but its relationships with the mathematical representation of objectives, and implications of tradeoffs for Pareto optimal decisions a...

Hydropower dams are a source of renewable energy, but dam development and hydropower generation negatively affect freshwater ecosystems, biodiversity, and food security. We assess the effects of hydropower dam development on spatial–temporal changes in fish biodiversity from 2007 to 2014 in the Sekong, Sesan, and Srepok Basins—major tributaries to...

Agricultural irrigation practices have changed through time as technology has enabled more efficient conveyance and application. In some agricultural regions, irrigation can contribute to incidental aquifer recharge important for groundwater return flows to streams. The Henrys Fork Snake River, Idaho (United States) overlies a portion of the Easter...

Dams and reservoirs are often needed to provide environmental water and maintain suitable water temperatures for downstream ecosystems. Here, we evaluate if water allocated to the environment, with storage to manage it, might allow environmental water to more reliably meet ecosystem objectives than a proportion of natural flow. We use a priority-ba...

Recent research suggests that removing underperforming, dangerous, and obsolete dams and barriers improves climate resilience to flooding, drought, hydrologic variability, and changing habitat conditions. Key benefits include reconnecting rivers, providing fish and wildlife access to cooler water in headwater reaches, and eliminating the risks pose...

Aquatic habitat suitability models are increasingly coupled with water management models to estimate environmental effects of water management. Many types of habitat models exist, but there are no standard methods to compare predictive performance of habitat model types for use with water management models. In this study, we compared three common a...

This report is part of a larger project to better understand how institutional context affects the potential for water markets to enhance climate resilience for agriculture and ecosystems, what legal and organizational features are likely to facilitate fair and effective water markets in the U.S. Southwest, and where opportunities exist to adapt ex...

Groundwater return flow to streams is important for maintaining aquatic habitat and providing water to downstream users, particularly in irrigated watersheds experiencing water scarcity. However, in many agricultural regions, increased irrigation efficiency has reduced return flows and their subsequent in‐stream benefits. Agricultural managed aquif...

Fish from Cambodia's Tonle Sap Lake are economically, culturally, and nutritionally significant for people in the Lower Mekong Basin, providing income, livelihoods, and protein. Fish in this system generally migrate toward upstream Mekong River in dry season and return in early wet season. However, drivers of fish migration from Tonle Sap Lake to t...

The Measurement Infrastructure Gap Analysis in Utah’s Great Salt Lake Basin was a comprehensive inventory and analysis of existing diversion and stream measurement infrastructure along 19 primary river systems, as well as a preliminary investigation of measurement infrastructure gaps around Great Salt Lake proper. The purpose of this “Gap Analysis”...

The goal of this project was to represent aquatic habitat with multiple environmental attributes to solve the problem of quantifying aquatic habitat in water resources system modeling for robust decision-making. Specific goals were to: 1) Test the accuracy and generality of publicly-available, large spatial scale environmental data to represent aqu...

Reservoirs are sometimes managed to meet agricultural and other water demands, while also maintaining streamflow for aquatic species and ecosystems. In the Henrys Fork Snake River, Idaho (USA), irrigation‐season management of a headwater reservoir is informed by a flow target in a management reach ~95 km downstream. The target is in place to meet i...

Predictive models are widely used to investigate relationships between the distribution of fish diversity, abundance, and the environmental conditions in which they inhabit, and can guide management actions and conservation policies. Generally, the framework to model such relationships is established; however, which models perform best in predictin...

Drought is a natural hazard that stresses ecosystems, agricultural production, food security, and local economies. Given ongoing hydropower dam development in the Sesan and Srepok Basins, the two most dammed tributaries in the Lower Mekong Basin, characterizing baseline drought events and understanding how dams modify downstream flow is needed to m...

Generalizable methods that identify suitable aquatic habitat across large river basins and regions are needed to inform resource management. Habitat suitability models intersect environmental variables to predict species occurrence, but are often data intensive and thus are typically developed at small spatial scales. This study estimated mean mont...

Utah’s Great Salt Lake is a treasured resource, yet dedicated flows have not been established to preserve the economic, ecological, and cultural values that the lake provides. Utah’s prior appropriation law allocates water rights based on time of first use, meaning agricultural water uses typically have senior rights. Utah’s Water Banking Act, whic...

Making the environment an operational priority is a better way to manage rivers with large, multi-purpose reservoirs. This entails giving the environment a water budget—with assets including a share of both inflow and storage space in the reservoir. This water budget functions like a high-priority water right. Our modeling shows that having both wa...

Large reservoirs like those that rim the Central Valley are essential for managing water in California’s highly variable climate. They provide multiple benefits including water supply, hydropower, flood management, and recreation. However, construction and operation of these reservoirs have also imposed significant environmental costs, including na...

Key Takeaways Large reservoirs like those that rim the Central Valley are essential for managing water in California’s highly variable climate. They provide multiple benefits including water supply, hydropower, flood management, and recreation. However, construction and operation of these reservoirs have also imposed significant environmental costs...

Public concern over environmental issues such as ecosystem degradation is high. However, restoring coupled human-natural systems requires integration across many science, technology, engineering, management, and governance topics that are presently fragmented. Here, we synthesized 544 peer-reviewed articles published through September 2020 on the d...

The project developed and validated statewide habitat suitability models for Bonneville cutthroat trout (Oncorhynchus clarki utah) and bluehead sucker (Catostomus discobolus) in Utah using publicly-available, large spatial scale geospatial data. Specific objectives included: 1) Represent aquatic habitat suitability by intersecting environmental da...

Global warming intensifies the hydrological cycle by altering the rate of water fluxes to and from the terrestrial surface, resulting in an increase in extreme precipitation events and longer dry spells. Prior hydrological intensification work has largely focused on precipitation without joint consideration of evaporative demand changes and how pla...

Methods that accurately identify suitable aquatic habitat for large regions and are generalizable to other regions are needed to inform resource management. Habitat suitability models intersect environmental variables to predict species occurrence, but are often data intensive and thus typically developed for small spatial extents. This study estim...

Plain Language Summary Lakes are an important component of arctic ecosystems. Arctic lake thermal processes have recently experienced dramatic changes due to climate warming. Thorough integration of observations and modeling results at the whole‐lake scale is needed to better understand warming effects on arctic lakes. We chose an arctic lake to co...

The goal of this project is to develop and validate a statewide habitat suitability model for Bonneville cutthroat trout (Oncorhynchus clarki utah) and bluehead sucker (Catostomus discobolus) in Utah using publicly-available, large spatial scale environmental data (GIS and remotely-sensed datasets). This enables management goals of modeling, identi...

Adaptation gaps arise when observed adaptation to climate change is slower than perceived adaptation potential. Two common explanations for adaptation gaps are (1) private parties failing to recognize that the climate is changing and (2) the cost of adaptation is higher than commonly believed. This paper shows how these two explanations are linked...

Tonle Sap lake-river floodplain ecosystem (TSE) is one of the world’s most productive freshwater systems. Changes in hydrology, climate, population density, and land use influence water quality in this system. We investigated long term water quality dynamics (22 years) in space and time and identified potential changes in nutrient limitation based...

Establishing reference conditions in rivers is important to understand environmental change and protect ecosystem integrity. Ranked third globally for fish biodiversity, the Mekong River has the world’s largest inland fishery providing livelihoods, food security, and protein to the local population. It is therefore of paramount importance to mainta...

Study Region Lake Urmia, Iran. Study focus There is widespread interest in restoring drying saline lakes. At Iran’s hypersaline Lake Urmia, managers have sought a uniform target lake level of 1274.1 m above sea level to lower salinity below 263 g L⁻¹ and recover Artemia to sufficient densities to support flamingos. We suggest that addressing a bro...

The Mekong River is one of the world’s largest rivers, unparalleled in terms of its biodiversity and ecosystem services. As in other regions, sufficient water quality is required to support diverse organisms, habitats, and ecosystems, but in the Mekong region, water quality has not been well studied. Based on biological and physical-chemical data c...

Mountain pine beetle (MPB; Dendroctonus ponderosae Hopkins) causes extensive tree mortality in whitebark pine (Pinus albicaulis Engelm) forests. Previous studies conducted in lodgepole pine (Pinus contorta Douglas), Douglas-fir (Pseudotsuga menziesii (mirb.) Franco), and Engelmann spruce (Picea engelmanni Parry ex. Engelm) have shown that litter, d...

In Mekong riparian countries, hydropower development provides energy, but also threatens biodiversity, ecosystems, food security, and an unparalleled freshwater fishery. The Sekong, Sesan, and Srepok Rivers (3S Basin) are major tributaries to the Lower Mekong River (LMB), making up 10% of the Mekong watershed but supporting nearly 40% of the fish s...

Glaciers provide cold, turbid runoff to many mountain streams in the late summer and buffer against years with low snowfall. The input of glacial meltwater to streams maintains unique habitats and support a diversity of stream flora and fauna. In western Canada, glaciers are anticipated to retreat by 60-80% by the end of the century, and this retre...

The Mekong River is a globally important river system, known for its unique flood pulse hydrology, ecological productivity, and biodiversity. Flooded forests provide critical terrestrial nutrient inputs and habitat to support aquatic species. However, the Mekong River is under threat from anthropogenic stressors, including deforestation from land c...

Great Salt Lake (GSL) covers 5500 km² (2100 mi²) at its unimpacted elevation and is the eighth largest saline lake in the world. Its highly productive food web supports millions of migratory birds and the economic value of the lake is estimated at $1.5 billion US dollars in 2019. Droughts and wet cycles have caused huge fluctuations in lake level,...

Utah's Great Salt Lake covers 5500 km 2 (2100 mi 2) at its unimpacted elevation and is the eighth largest saline lake in the world. Its highly productive food web supports millions of migratory birds and the economic value of the lake is estimate at $1.5 billion in 2019 U.S. dollars. Droughts and wet cycles have caused huge fluctuations in lake lev...

Managed aquifer recharge (MAR) is typically used to enhance the agricultural water supply but may also be promising to maintain summer streamflows and temperatures for cold-water fish. An existing aquifer model, water temperature data, and analysis of water administration were used to assess potential benefits of MAR to cold-water fisheries in Idah...

More than 5 million people live near Lake Urmia in northwestern Iran. Urmia is one of the world’s largest hypersaline lakes, yet over the past two decades, the lake has lost 95% of its volume and the lake level has dropped more than 7 m. We synthesized 40 years of available data, defined 10 management objectives for human health, water quality, eco...

The goal of this project is to develop and validate a statewide habitat suitability model for Bonneville cutthroat trout (Oncorhynchus clarki utah) and bluehead sucker (Catostomus discobolus) in Utah using publicly-available, large spatial scale environmental data (GIS and remotely-sensed datasets. This enables management goals of modeling, identif...

Managing regulated rivers usually considers both economic and ecological benefits. Decision-making involves tradeoffs, conflicts, compromise, and cooperation among competing objectives. Pareto-optimality is frequently advocated for water management, but how the mathematical representation of tradeoffs affects decisions and tradeoffs is rarely exami...

Low-flow targets are important for maintaining aquatic habitat amid multi-stakeholder water use, but can also create conflict among users. A collaborative management group in the Henry’s Fork watershed, a tributary to the upper Snake River, recommends strategies for reservoir operations to meet a downstream low-flow target during irrigation season....

The timing of thermal patterns have important implications for ecosystem functions. Understanding how temporal patterns may vary in different thermal regimes can improve understanding of physical and ecological feedbacks. We analyzed annual stream temperature patterns for reaches with canopy cover ≥ 70% with cover gaps ≤ 6 km using sine functions f...

We improved lake mixing process simulations by applying a vertical mixing scheme, K profile parameterization (KPP), in the Community Land Model (CLM) version 4.5, developed by the National Center for Atmospheric Research. Vertical mixing of the lake water column can significantly affect heat transfer and vertical temperature profiles. However, the...

Managed aquifer recharge (MAR) is currently being used in the Snake River basin, USA to stabilize and enhance water supply for agriculture, municipal use, and hydropower. In part because of favorable hydrogeology, MAR also provides a promising tool for mitigating effects of climate change on the basin’s valuable fish and wildlife resources. MAR can...

The Mekong River is characterized by large-scale fish migrations, which support approximately 65 million people. Rapid hydropower development is providing energy for developing countries, but is also threatening biodiversity and food security. The Se Kong, Se San, and Sre Pok Rivers (the 3S basin) are shared by Cambodia, Laos, and Vietnam and form...

Watershed-scale stream temperature models are often one-dimensional because they require fewer data and are more computationally efficient than two- or three-dimensional models. However, one-dimensional models assume completely mixed reaches and ignore small-scale spatial temperature variability, which may create temperature barriers or refugia for...

We improved lake mixing process simulations by applying a vertical mixing scheme, K profile parameterization (KPP), in the Community Land Model (CLM) version 4.5, developed by the National Center for Atmospheric Research. Vertical mixing of the lake water column can significantly affect heat transfer and vertical temperature profiles. However, the...

A recent article reviewed data on Great Salt Lake (Utah) and concluded falsely that climate changes, especially local warming and extreme precipitation events, are primarily responsible for lake elevation changes. Indeed climatically influenced variation of net inflows contribute to huge swings in the elevation of Great Salt Lake (GSL) and other en...

Meng (2019) reviewed data on Great Salt Lake (Utah) and concluded falsely that climate changes, especially local warming and extreme precipitation events are primarily responsible for the elevation changes in this, and other saline lakes worldwide. Meng is correct that climatically influenced variation of net inflows contribute to huge swings in th...

There is growing evidence that flood mitigation is often inefficient because individuals misestimate flood risk. The propensity to misestimate flood risk is expected to rise because climate change ensures the past will be a poor predictor of the future. Greater reliance on downscaled climatological and hydrological forecasts has been suggested to a...

Rivers provide multiple water uses and services, including offstream uses that are valued economically and instream uses, such as recreation and ecosystem preservation, that are rarely valued economically. In many countries, water rights allocate water to offstream uses, and dedicated minimum instream flows are the main instrument for instream wate...

Environmental objectives often poorly represented in water resources systems models, although water management is sometimes driven by environmental objectives and regulations. The goal of this research is to a) better represent environmental objectives, 2) identify a simple and generalizable approach for water resources systems modeling, and 3) dev...

Understanding how the distribution of forests might respond, expand, or compress is important for forest and water management. Climate change is predicted to affect the distribution of tree species and forests in mountain regions. Effects may be especially acute in mountain environments as warming temperatures drive montane and alpine ecosystems up...

Watershed-scale stream temperature models are often one-dimensional because they require less data and are more computationally efficient than two- or three-dimensional models. However, one-dimensional models assume completely mixed reaches and ignore small-scale spatial temperature variability, which may create temperature barriers or refugia for...

The world's saline lakes are shrinking and human water diversions are a significant contributor. While there is increased interest in protecting the ecosystem services provided by these lakes, the cost of protecting water levels has not been estimated. To explore this question we consider the case of Great Salt Lake (Utah, USA) where human diversio...

Significance Climate change is expected to alter streamflow volume and variability in watersheds throughout the world, which will have impacts on agricultural, aquatic, and urban environments. Human modifications such as the building of reservoirs and the extraction of water for agricultural and urban uses, however, are thought to mask climate-indu...

Representing urban water demands economically is useful to understand how anticipated changes like population growth, conservation, water development, climate change, and environmental water demands may affect water deliveries and scarcity. Utah is the second driest state in the nation, while per capita water use is near the highest in the nation,...

In their article “Designing river flows to improve food security futures in the Lower Mekong Basin” (8 December, p. 1270), J.L. Sabo et al. use a questionable modeling approach to show that manipulating Mekong River flows using stored water may enhance fisheries yield. Their work underscores operating dams to maximize yield but, as they point out,...

Researchers and water managers have turned to green stormwater infrastructure, such as bioswales, retention basins, wetlands, rain gardens, and urban green spaces to reduce flooding, augment surface water supplies, recharge groundwater, and improve water quality. It is increasingly clear that green stormwater infrastructure not only controls stormw...

Many of the world's saline lakes are shrinking at alarming rates, reducing waterbird habitat and economic benefits while threatening human health. Saline lakes are long-term basin-wide integrators of climatic conditions that shrink and grow with natural climatic variation. In contrast, water withdrawals for human use exert a sustained reduction in...

Swaner Preserve Instream Flow and Habitat Report

The objective of our work in Phase III of the Walker Basin Research Project was to expand habitat and water quality monitoring and modeling, understand Walker River environmental and biological relationships to guide restoration, and highlight Walker River reaches and time periods with suitable trout habitat from potential environmental water purch...

Stormwater Management and Ecosystem Services: A Literature Review

Quantifying thermal variability to inform restoration in Nevada’s Walker River

Instream barriers, such as dams, culverts and diversions are economically important for water supply, but negatively affect river ecosystems and disrupt hydrologic processes. Removal of uneconomical and aging in-stream barriers to improve habitat connectivity is increasingly used to restore river connectivity. Most past barrier removal projects foc...

Water year types (WYTs), whereby years are classified by river runoff quantity compared to historical runoff, are one tool to help make major water management decisions. Increasingly, these decisions include instream flow requirements (IFRs) below dams for river ecosystem management. However, WYTs are typically based on assumptions of stationarity,...