Instream Flow Research Articles

Adapting generalized suitability curves from Brown trout to Minnow using 1D and 2D aquatic habitat models

The article focuses on adapting generalized depth preference and flow velocity characteristics from Brown trout (Salmo trutta morpha fario) to the Minnow (Phoxinus phoxinus). The results obtained were used to model habitat suitability with 1D and 2D models. Since 1995, research on assessing aquatic habitat quality has been ongoing on 77 mountain streams in Slovakia. This assessment employs a System of Environmental Flow Analysis (SEFA), which is based on the Instream Flow Incremental Methodology (IFIM). In most sections, Brown trout occurred in representative numbers. Brown trout habitat preferences were derived and generalized, and represented by suitability curves. Minnows were present in sufficient numbers for the derivation of suitability curves only on some streams, making direct generalization from the measured data unrepresentative. The measurement results showed that Minnow has similar depth and flow rate preferences to Brown trout. Therefore, it can be assumed that it is possible to adapt the generalised suitability curves from Brown trout to Minnow. This expansion enabled us to broaden the assessment of habitat quality using the SEFA model to mountain streams that are dominated by Minnows and where there is insufficient Brown trout presence. Verification of parameter adaptation from Brown trout to Minnow was conducted in 11 sections of mountain streams. We discuss the performance of habitat quality modeling, concerning the fundamental hydraulic characteristics of streams, using both 1D and 2D models. The results of the 2D modeling are presented for a sub-mountain stream.

Evaluation of Water Allocation Scenarios in the Seomjin River Watershed Based on CMIP6 Scenarios

This study evaluated the impact of climate change and water allocation scenarios on water security in the Seomjin River Basin using K-WEAP (Korea-Water Evaluation and Planning System). The findings indicated that domestic water and instream flow are vulnerable to climate change, while industrial water supply may fail to meet future demand in certain regions. Moreover, prioritizing instream flow was found to compromise the stability of the domestic water, and equal allocation adversely affected both domestic and industrial water security. Consequently, maintaining the current system appears to be the most effective approach; however, future studies should focus on developing flexible strategies that consider the effects of climate change and regional characteristics in a more detailed manner.

Channel restoration in urbanized systems: Guiding design using ecological flow targets and future management scenarios

AbstractRestoration of urban rivers must simultaneously design for ecological habitat while accounting for altered flow regimes associated with urban runoff, flood protection, and industrial/wastewater discharge. The goal of this study was to use ecological flow targets to guide channel restoration of the Los Angeles (LA) River across potential future flow regimes. Using a one‐dimensional hydraulic model, we simulated a range of channel cross section configurations subject to different flow management decisions (wastewater reuse, low‐flow [LF] treatment, and baseflow augmentation). Hydraulic results were assessed relative to ecohydraulic targets for desirable aquatic species in the LA River (willow, steelhead trout, and Santa Ana sucker). Results suggest that, along the mainstem of the LA River, restoration designs that include narrow LF channels may support Santa Ana sucker habitat and steelhead migration if management decisions decrease instream flows (e.g., by reusing treated wastewater). However, the same channel design and management decisions may not provide conditions needed to propagate floodplain vegetation such as willows. In tributary reaches, flows are too low to support habitat conditions for Santa Ana sucker or steelhead but may be able to support riparian habitat if a soft‐bottom LF channel and active floodplain are present. In general, results illustrate the trade‐offs between water management goals and habitat requirements for target species.

Discharge and sediment load modeling using rating curve-based missing data management

ABSTRACT Hydrological models are vital for water management to determine in-stream flow, irrigational water, domestic water supply, and biodiversity conservation. This study formulates a hydrological model with a novel approach for streamflow and sediment load in the QGIS-supported Soil and Water Assessment Tool for the Halda River catchment, a unique ecological habitat for natural carp spawning and freshwater sources. The daily simulation uses an innovative stage–discharge relationship technique from available 15-day interval flow data. The model evaluation parameters R2 values 0.80 and 0.62, and NS values 0.81 and 0.61 for calibration and validation of streamflow suggested excellent agreement in the seasonal cycle and most of the monsoon peak flow. The streamflow/precipitation ratio indicates a significant influence of groundwater through infiltration. The baseflow shows a decreasing trend. The sediment load based on suspended sediment concentration at a downstream location is 1,625 tons/day. On the contrary, the model prediction is 30 times lower. The scattered sediment load data support the model estimate by considering relatively lower intervention or land use change in its upstream. This model provides a baseline for daily flow and sediment load for scenario modeling (e.g., climate change, land use change) for environmental flow estimation of the fish habitat, freshwater supply, irrigation, and salinity intrusion.

Working (around/within/against) prior appropriation: Diverse hydrosocial practices to secure water for rivers

Water scarcity in the Western US, through the lens of political ecology, can be understood as inextricably shaped by power dynamics, governance structures, and legal practices of resource allocation. Water allocation in the region is determined largely by the legal doctrine of Prior Appropriation, the 'first in time, first in right' principle. However, prior appropriation is fundamentally based in anthropocentric and settler colonial assumptions, and in light of drought, climate change, and shifting social and environmental values, the system has been critiqued as inadequate to meet contemporary water challenges. Despite challenging historical legacies, water managers in the Western US are developing a range of strategies to work around or within prior appropriation to secure environmental flows for rivers and aquatic species. In this article we use political ecology and diverse economies approaches to consider the challenges of, and challenges to, prior appropriation. We examine a diverse set of practices, work-arounds, and creative strategies being used to secure instream flows, and discuss how these strategies affirm or challenge prior appropriation, how they reinforce or challenge inequities, and how they reform or re-envision water allocation in ways that may open up potential for social and environmental justice.

Characterizing streamflow regimes using a distributed model for sustainable resource management in the humid tropics

Estimating streamflow regimes on small tropical islands is challenging due to limited observational data, poor accuracy of remote sensing, and the limitations of coarse-scale climate models, restricting our understanding of hydrological processes and the management of water resources. The inadequacy of data has also affected the development of instream flow standards (i.e., environmental flows, e-flows) needed to protect ecological and cultural values central to island communities. Estimates of water availability for agriculture, hydropower, and drinking water supply are also critical for informed investments in water resource planning. We utilized high-resolution (250 m) gridded daily rainfall data to parameterize the Soil and Water Assessment Tool (SWAT) to characterize streamflow regimes at ungauged locations in a watershed on Kaua‘i Island. The resultant flow statistics were then used to describe the daily, seasonal, and annual availability of surface water to evaluate the implications of potential e-flow scenarios on water available for run-of-river hydropower. Compared to rainfall data derived from a single station within the watershed, the gridded daily rainfall product increased the accuracy of model output from not satisfactory to good. Model techniques using high resolution rainfall data may substitute for long-term hydrological data collection across complex tropical environments and provide data for making sustainable management decisions at ungauged locations.

Using Financial Contracts to Facilitate Informal Leases Within a Western United States Water Market Based on Prior Appropriation

AbstractThe ability to reallocate water to higher‐value uses during drought is an increasingly important “soft‐path” tool for managing water resources in an uncertain future. In most of the Western United States, state‐level water market institutions that enable reallocation also impose substantial transaction costs on market participants related to regulatory approval and litigation. These transaction costs can be prohibitive for many participants in terms of both costs and lengthy approval periods, limiting transfers and reducing allocation efficiency, particularly during drought crises periods. This manuscript describes a mechanism to reduce transaction costs by adapting an existing form of informal leases to facilitate quicker and less expensive transfers among market participants. Instead of navigating the formal approval process to lease a water right, informal leases are financial contracts for conservation that enable more junior holders of existing rights to divert water during drought, thereby allowing the formal transfer approval process to be bypassed. The informal leasing approach is tested in the Upper Colorado River Basin, where drought and institutional barriers to transfers lead to frequent shortages for urban rights holders along Colorado's Front Range. Informal leases are facilitated via option contracts that include adaptive triggers and that define volumes of additional, compensatory, releases designed to mitigate impacts to instream flows and third parties. Results suggest that more rapid reallocation of water via informal leases could have resulted in up to $222 million in additional benefits for urban rights holders during the historical period 1950–2013.

Evaluation of water shortage and instream flows of shared rivers in South Korea according to the dam operations in North Korea

Abstract The Korean Peninsula's mountainous terrain poses challenges to effective water resource management. Notably, two significant river basins, North Han River and Imjin River basins, are essentially shared rivers originating in North Korea. After the construction of various dams in North Korea, billions of tons per year of water annually decreased from the upper reaches of these rivers of North Korea to South Korea. This study conducted an impact analysis on two major river basins affected by dam operations in North Korea. Both before and after the Imnam Dam operation, significant reduction (27.7%) in the average monthly inflow was observed, and the total release of the Hwacheon Dam in South Korea decreased by 40.2%. The analysis of instream flow indicated that the operation of dams in North Korea had a substantial impact on fulfilling instream flow requirements for dams located in North Han River and Imjin River basins. To ensure instream flow, this study proposed two plans. The first plan involved the utilization of existing dams in the North Han River basin, while the second plan suggested connecting the dams in North Korea, taking into account the shared rivers.

Moving Water

Climate change-induced megadrought and rapid urbanization are forcing western agriculture into retreat as water supplies diminish and heat and drought ravage crops and livestock. At the same time, the megadrought is imposing deep ecological harm on riparian areas, fish species, and soil and increasing the concentration of pollutants in dwindling waterways. These developments raise the question of how to use the water rights left behind as western irrigated agriculture in-evitably shrinks. We argue that federal purchase of some of these rights could create a pool of water available for instream flows (also termed environmental flows) to preserve waterways and aquatic eco-systems. We propose that the federal government acquire some west-ern water rights from agricultural holders, just as it has acquired homes in residential “managed retreat” programs, and dedicate those rights to instream flows. This proposal is novel in agricultural policy, which has stubbornly subsidized agriculture in place, and in the schol-arship on government managed retreat from climate change, which has focused on retreating people and land, not rights in natural re-sources. Federal government managed retreat of western water rights reasserts a federal role in western water allocation, a feature we con-tend accords with current needs as well as history. The allocation of western water and the system of state and private water ownership are largely the result of the post-Civil War response to illegal gold and silver mining thought necessary to encourage western settlement. These policies no longer respond to the modern urbanized West and its present environmental challenges. Drought retreat presents an oppor-tunity for the federal government to move toward a more balanced al-location of western water and create durable environmental benefits.

Modeling Landscape Influence on Stream Baseflows for Watershed Conservation

Instream flows are vital to the ecology of riverine and riparian systems. The influence of watershed characteristics on these systems is helpful in developing landscape policies to maintain these flows. Watershed characteristics like precipitation, forest cover, impervious cover, soil drainage, and slope affect baseflows. Spatial analysis using GIS and nonlinear regression analysis is used to analyze spatial and temporal information from gauged watersheds in Massachusetts to quantify the relationship between baseflows and watershed metrics. The marginal functions of landscape factors that reflect changes in baseflow are quantified. This information is then applied to watershed policy toward improving base flows. The interactions of three fixed attributes, soil drainage, rainfall incidence, and slope, are analyzed for the manageable landscape attributes of impervious and forest cover. Developing watershed policy to protect baseflows involves evaluating the complex interactions and functional relationships between these landscape factors and their use in watershed conservation planning.

Water Supply Planning in the Face of Drought and Ecosystem Flows: Examining the Impact of the Bay-Delta Plan on Bay Area Water Supply.

In California, recent Bay-Delta Plan legislation attempts to balance water supply and ecosystem protection by requiring 40% of the flow to remain in-stream in the Tuolumne River from February through June. Serious questions remain about what this means for the Bay Area water supply, especially during drought. Our work develops a new approach to analyze how in-stream flow policy coupled with climate change could impact regional water supply over the coming decades. Results show that the new in-stream flow demand would exceed urban water deliveries in a typical year. In wet years, water supply performance is minimally impacted, but in drought, the policy can lead to less water in storage, delayed reservoir recovery, and increased time at critically low storage. Storage impact exceeding 50 000 acre-feet (60 million m3) is anticipated with at least 18% frequency, demonstrating that, climate uncertainty notwithstanding, this impact must be planned for and managed to ensure a reliable future water supply.

Evaluation of alternative approaches to PHABSIM modeling of coastal cutthroat trout spawning habitat

AbstractIn the face of a changing climate and increasing human demand for water, an understanding of habitat preference has become critical for managing wild fish populations and projecting potential changes in habitat and populations. Two approaches to Physical Habitat Simulation (PHABSIM) modeling of coastal cutthroat trout Oncorhynchus clarkii clarkii spawning habitat were compared by modeling a reach, consisting of eight transects covering a pool and upstream and downstream riffles, of a small Puget Sound stream with two sets of habitat variables. The reach contained a cluster of redds 2 years in a row, assumed to be an indication of preferred spawning habitat and was located in the area of maximum spawning in the watershed, based on multiple years of redd surveys. Two PHABSIM instream flow models of the study site, one based on standard microhabitat (depth [D], velocity [V], and substrate [S]) suitabilities and the other based on D, V, and channel unit (CU) suitabilities, were developed and compared for their relative ability to correctly predict coastal cutthroat trout spawning habitat selection at the redd cluster within the PHABSIM study site. One approach was the standard use of habitat suitability criteria (HSC) for D, V, and S to indicate spawning habitat quality. The alternate approach was to replace substrate HSC with CU index HSC that incorporated dominant substrate particle diameter, CU (riffle, deep and shallow pool tail, pool body, deep and shallow pool edge, cascade, waterfall, and terrestrial), where deep and shallow units were based on relative residual depth (RRD), size of CU relative to channel width, and position within CU. Spawning habitat quality was calculated for each transect as weighted usable width with the standard HSC metrics (WUWs) as well as the modified CU index (WUWm). WUWm at the transects bracketing the redd cluster exceeded WUWm at the remaining six transects and was outside the 95% confidence interval for WUWm at the remaining transects. In contrast, WUWs varied less between the redd cluster and the remainder of the transects, suggesting the CU index better reflected spawning habitat quality than substrate. Incorporation of elevation relative to SZF addressed vulnerability to declining flow during incubation. Both models resulted in maximum WUA within the range of discharges that coincided with the majority of fresh cutthroat trout redds in Skookum Creek.

Concurrently assessing water supply and demand is critical for evaluating vulnerabilities to climate change

AbstractAligning water supply with demand is a challenge, particularly in areas with large seasonal variation in precipitation and those dominated by winter precipitation. Climate change is expected to exacerbate this challenge, increasing the need for long‐term planning. Long‐term projections of water supply and demand that can aid planning are mostly published as agency reports, which are directly relevant to decision‐making but less likely to inform future research. We present 20‐year water supply and demand projections for the Columbia River, produced in partnership with the Washington State Dept. of Ecology. This effort includes integrated modeling of future surface water supply and agricultural demand by 2040 and analyses of future groundwater trends, residential demand, instream flow deficits, and curtailment. We found that shifting timing in water supply could leave many eastern Washington watersheds unable to meet late‐season out‐of‐stream demands. Increasing agricultural or residential demands in watersheds could exacerbate these late‐season vulnerabilities, and curtailments could become more common for rivers with federal or state instream flow rules. Groundwater trends are mostly declining, leaving watersheds more vulnerable to surface water supply or demand changes. Both our modeling framework and agency partnership can serve as an example for other long‐term efforts that aim to provide insights for water management in a changing climate elsewhere around the world.

The value of improving freshwater ecosystem services: South Carolina residents’ willingness to pay for improved water quality

Riverine ecosystems play a crucial role in providing essential services such as drinking water, food, recreation, and other aquatic resources. Yet, their capacity to deliver ecosystem services is threatened by rapid land use which modifies their ecological functions. While freshwater monitoring and restoration programs became more robust with technological advancement, the technical ecosystem indicators monitored by experts do not typically resonate with the public. Since public sentiments and preferences are crucial in conservation planning, we quantified households' mean willingness to pay (WTP) for riverine ecosystem services in South Carolina (SC) using a payment card approach. This technique in conducting a contingent valuation method allowed us to estimate mean WTP for five aquatic indicators. Findings revealed that households’ monthly mean WTP is higher for indicators that can enhance recreational benefits, such as fish catch ($5.89- $6.58), species richness ($6.28- $6.72) and access ($6.75) compared to IBI ($5.74- $6.26) and instream flow quality ($5.34–6.06). When extrapolated to entire SC, the improvement of each indicator would translate to total benefits ranging between $131 to $165 million annually. The values computed from this study could serve as inputs for the computation of benefit-cost ratios of proposed freshwater programs. By incorporating households' WTP in the policy analysis, decision makers can prioritize programs that offer the greatest public benefit, while enhancing freshwater quality across the state.

Stream Flow Management and Institutions: Studying Water Quality and Aquatic Ecosystems in Dry Seasons

Stream flow management during the dry season involves balancing human water needs with the environmental requirements of the river. The allocation of stream water flow is determined by considering 10-year frequency low flow as the total available water amount, with instream flow adopted to consider the flow requirements of the river environment. However, conflicts arise over water rights between human users and the river environment during water scarcity. This study conducted an empirical-based analysis of minimum flow for river environments, focusing on water quality and aquatic ecosystems. Additionally, the perceptions of stakeholders of securing and using stream flow were investigated through a questionnaire. The outcomes of this study can contribute to enhancing technical methods for calculating instream flow and improving systems for managing river water during dry seasons.

Evaluation and securing of ecological flow by linking fish growth scenarios and basin water budget analysis

Maintaining ecological flow is crucial for preserving healthy aquatic ecosystems. This study presents a novel approach to assess and secure ecological flow by linking fish growth scenarios with water budget analysis. Addressing the challenges of accurately predicting ecological flow requirements, especially in post-dam-construction scenarios, is a central focus. In the Gam River basin, we assess the compatibility of a target fish species with post-dam quantitative instream flow, confirming an appropriate 4 m3/s for Zacco platypus in the basin's water supply system. This determination, facilitated by the K-WEAP model, not only ensures water availability but also prevents the Gimcheon-Buhang Dam from falling below its dead storage water level. Our study's key achievements include the development and successful application of this innovative methodology, integrating basin water budget analysis with fish population growth predictions across varying flow conditions. This approach allows the identification of potential ecosystem risks like water scarcity or pollution and determines the optimal ecological flow needed for maintaining the river ecosystem. Our research provides valuable insights for future endeavors in sustainable water resources management and river ecosystem conservation efforts.

Detection and Analysis of the Variation in the Minimum Ecological Instream Flow Requirement in the Chinese Northwestern Inland Arid Region by Using a New Remote Sensing Method

With the development of human society, the balance between the minimum ecological instream flow requirement (MEIFR), which is an essential part of the ecological water demand in arid areas, and anthropogenic water depletion has received increasing attention. However, due to the lack of hydrological station data and river information on arid basins, previous researchers usually considered only the individual ecological water demand of rivers, lakes, or oases. To address this issue, a new method that combines river hydraulic parameters and the wet circumference obtained by an unmanned aerial vehicle (UAV) and remote sensing hydrological station (RSHS) technologies was applied to obtain the MEIFR and, then, systematically and quantitatively explore the balance from the perspective of the entire basin of Aiding Lake from 1990 to 2022, which is the lowest point of Chinese terrestrial territory. The results showed the following: (1) since 1990, the discharge of the seven rivers in the study area increased by 1–6%, and the MEIFR of these rivers increased by 15–100%; both quantities decreased by 3–5% from the upper to the lower reaches of the basin; (2) the surface area and water level of Aiding Lake decreased by 5% and 14%, respectively, but the MEIFR first decreased by 25% from 1990 to 2013 and, then, increased by 66.7% from 2013 to 2022; and (3) from 2011 to 2022, the MEIFR and anthropogenic water depletion exhibited a balance. Against the background of climate change, this research revealed that the MEIFR of the rivers in the Aiding Lake Basin have shown an upward trend over the past 30 years and quantitatively determined the above balance relationship and the period of its occurrence. This study supplied a method that could provide guidance for water resource management by decision-makers at a global level, thus helping achieve the sustainable development goals (SDGs).

Sustainability assessment of small hydropower from an ESG perspective: A case study of the Qin-Ba Mountains, China

Small hydropower (SHP) has made significant contributions to economic and social development in rural and remote mountainous regions. However, the adverse ecological-environmental impacts resulting from the SHP sector and challenges in hydropower management have become major areas of concern. From an Environmental, Social, and Governance (ESG) perspective and using three SHP stations (GXD, WZL, and SJB) in the Qin-Ba Mountains as case studies, we constructed a sustainability assessment system comprising 18 indicators across three dimensions. The hesitant fuzzy linguistic term sets (HFLTSs) and cloud models were employed to determine the sustainability level of SHP by characterizing the hesitancy of the evaluator and the uncertainty of the evaluated data. (1) The ecological-environmental protection (E) dimension was assigned the greatest weight, followed by the dimensions of social responsibility contribution (S) and corporate governance management (G). The weights of certain indicators, including the water qualification rate, river morphology maintenance, guaranteed rate of instream flow, comprehensive utilization, and production safety standardization grade were relatively high, conforming to the current context of green development prioritization in which ecological-environmental protection is of the utmost importance. (2) The overall sustainability levels of all three SHP stations were “good”, with the E-dimension contributing the most and the G-dimension contributing the least to the sustainability goal. (3) The GXD, WZL, and SJB stations were ranked first, second, and third, respectively, in terms of their sustainability scores. This study provides an innovative perspective for the sustainability assessment of SHP. The evaluation method can be generalized to encompass multi-attribute decision-making problems. The findings of this study can aid in addressing the shortcomings associated with SHP development and promote sustainability within the SHP industry.

Unveiling an Environmental Drought Index and its applicability in the perspective of drought recognition amidst climate change

As a complex natural disaster, drought encompasses significant and wide-ranging impacts on various environmental aspects. While meteorological, hydrological, agricultural, and socioeconomic droughts have been extensively studied, the scientific understanding of environmental droughts (the proposed fifth classification) remains relatively limited, hampering practical assessment efforts. To address this gap, the present study, for the first time, conducted a rigorous assessment of the applicability of a novel method, namely the heuristic method, in conjunction with a newly developed Environmental Drought Index (EDI). The present study thoroughly analyzed environmental drought events in India's Brahmani River basin, specifically focusing on the Jaraikela catchment. Firstly, the Minimum in-stream Flow Requirement (MFR) was determined using Tennant’s method to synthetically estimate discharge rates to maintain the optimum flow range during the historical period (1980–2014). Secondly, Drought Duration Length (DDL) was calculated by counting consecutive water deficit months with negative monthly Streamflow Rate (SFR) and MFR differences. Three General Circulation Models (GCMs) output ensembles, namely EC-Earth3, MPI-ESM1-2-HR, and MRI-ESM2-0, participating in CMIP-6, were used for past (1980–2014) and future periods (FP-1: 2015–2022, FP-2: 2023–2045) under emission scenarios SSP245 and SSP585. The HydroClimatic Conceptual Streamflow (HCCS) model was employed to simulate the historical and future SFR. Thirdly, the largest water deficit magnitude during DDL was used to estimate the Water Shortage Level (WSL). Finally, integrating DDL and WSL provided the EDI for each environmental drought event. Results demonstrated a strong correspondence between the simulated EDI obtained using MPI-ESM1-2-HR under SSP585 and the observed EDI values, thereby indicating the credibility of the EDI in assessing environmental droughts. Furthermore, the study found severe droughts (i.e., EDI-3) dominating (71–73% of all droughts; occurring during non-monsoonal months) during FP-2 under SSP585 across all three GCMs, differing from moderate droughts in SSP245 of FP-2, both scenarios of FP-1, and the historical period. Based on the findings, the study finally proposed several adaptive measures to mitigate the impacts of increasing environmental drought events in the catchment.

Trout bioenergetics as a process‐based tool to estimate ecological risk in a regulated river

AbstractBioenergetics models produce quantitative flow‐ecology relationships that summarize changes in habitat and food resources from altered flows. We used a drift‐foraging bioenergetics model to quantify the net rate of energetic intake (NREI) for trout above and below a water diversion. NREI is reduced by >95% below the water diversion in July–September, when up to 98% of unimpaired flows are diverted. We then used a risk‐based approach to estimate the maximum diversion rate, expressed as a percentage of unimpaired flow, that would produce NREI values that are not significantly lower than values under unimpaired flows throughout a 62‐year period. NREI decreased with increased precent‐of‐flow diversion rates in low‐flow months (July–September). Diversion rates of 16% in July and 9% in August and September would maintain NREI within the range of unimpaired flow conditions. In higher flow months, May–June, increasing diversions brought estimated instream flows closer to the peak NREI flow, leading to the assessment that increased diversions would increase NREI. Bioenergetic models can be used to develop protective flow rates at times of the year when fish growth and production would be high under unimpaired flows, which often coincides with when water is diverted. Our study is the first to develop protective percent‐of‐flow diversion rates for holistic flow management using a quantitative process‐based and fish‐centric ecological metric.