Health Of Riverine Ecosystems Research Articles

Elevation-associated pathways mediate aquatic biodiversity at multi-trophic levels along a plateau inland river

Aquatic biodiversity plays a significant role in maintaining the ecological balance and the overall health of riverine ecosystems. Elevation is an important factor influencing biodiversity patterns. However, it is still unclear through which pathway elevation influences riverine biodiversity at different trophic levels. In this study, the elevation-associated pathways affecting aquatic biodiversity at different trophic levels were explored using structural equation modeling (SEM) and taking the Bayin River, China as the case. The results showed that the elevational patterns were different among aquatic organisms at different trophic levels. For macroinvertebrates and bacteria, the pattern was hump-shaped; while for phytoplankton and zooplankton, it was U-shaped. Building upon these observed elevational patterns, our investigation delved into the direct and indirect pathways through which elevation influences aquatic biodiversity. We found that elevation exerts an impact on aquatic biodiversity via indirect pathways. For all aquatic organisms investigated, the major pathway through which elevation influences biodiversity is mediated by water temperature and water quality. For aquatic organisms at higher trophic levels, like macroinvertebrates and zooplankton, the crucial pathway is also mediated by the landscape. The results of this study contributed to understanding the effects of elevation on aquatic organisms at different trophic levels and provided an important basis for the assessment of riverine biodiversity at large scales.

Development of new assessment approach: a macroinvertebrates-based biotic scoring system to assess the health of riverine ecosystems in the Sahel area in Burkina Faso (West Africa)

To address ongoing threats from human pressures and climate changes, water managers and users require a visual tool that provides accurate information about the health of waterbodies for decision making. However, there is a lack of less sophisticated methods, such as biotic scoring, to assess the health of rivers in West Africa. To bridge this gap, we have developed a macroinvertebrate-based scoring system for monitoring the health of rivers in the Sahelian regions. We adopted a multi-habitat sampling approach to collect macroinvertebrates using hand nets, and these specimens were identified mostly to family taxonomic level using keys. We recorded more than 75 taxa of macroinvertebrates, each assigned relative sensitivity scores to human disturbances ranging from 1 (very tolerant) to 10 (highly sensitive). The Burkina Biotic Score System (BBIOSS) and the Average Score Per Taxa (ASPT) demonstrated a strong and significant correlation with environmental variables, including anthropogenic pressures types (r = 0.6; p < 0.01) making it a robust tool for monitoring rivers. Here, our findings revealed that all taxa scored are expected to be those reported in Western African freshwater. This study has produced an effective tool that can be used or adapted to monitor other riverine ecosystems in West Africa, potentially contributing to the preservation of water and biological resources.

Development, validation, and application of a microbial community-based index of biotic integrity for assessing the ecological status of a peri-urban watershed in China

This study represents the pioneering effort in employing 16S rRNA-bacteria and 18S rRNA-microeukaryotes to construct the microbial community-based index of biotic integrity (MC-IBI) for assessing the ecological health of riverine ecosystems. The MC-IBI was developed, validated, and implemented using water samples from the Changle River watershed, encompassing both wet and dry seasons. A total of 205 metrics, containing microbial diversity, composition, pollution tolerance/sensitivity, and functional categories, were selected as candidates for evaluation. Following a rigorous screening process, five core metrics were identified as key indicators, namely Pielou's evenness of microeukaryotes, %Cryptophyceae, %Proteobacteria, %Oxyphotobacteria, and % 16S rRNA gene-human pathogens. Moreover, redundancy analysis revealed three metrics (i.e., Pielou's evenness, % 16S rRNA gene-human pathogens, and % Proteobacteria) were positively correlated with impairment conditions. In contrast, two metrics (i.e., %Oxyphotobacteria and %Cryptophyceae) were associated positively with reference conditions. Notably, the developed MC-IBI demonstrates clear discrimination between reference and impaired sites and significantly correlates with environmental parameters and land use patterns. A path model analysis revealed that land use patterns (i.e., build-up land, cropland) negatively impacted the MC-IBI scores. The application of the MC-IBI method yielded an assessment of the ecological conditions at the 73 sampling locations within the Changle River watershed, assigning them into categories of “Very good” (4.1 %), “Good” (4.1 %), “Moderate” (5.5 %), “Poor” (21.9 %), and “Very poor” (64.4 %). This bioassessment framework presents an innovative approach toward the preservation, maintenance, and management of riverine ecosystems.

Testing and applying baseflow approaches to environmental flow needs

Environmental flow need (EFN) is defined as the quantity, quality, and timing of flow that are required to maintain the health of riverine ecosystems and human and societal sustainable development. Numerous research frameworks have been developed and used with a range of sophistication, data requirements, and management strategies. Recently, 90% of the monthly baseflow derived from groundwater has been proposed as the presumptive standard for the groundwater contribution of EFN. However, this proposed groundwater presumptive standard has not been compared to the field-based EFN, which limited its practical application in water management. Therefore, we ask whether baseflow can be used as an index of EFN, and if so, is 90% of monthly baseflow robust for aquatic ecosystems? We selected nine watersheds in the Okanagan Basin (Canada) with well-established EFN based on extensive fieldwork and local experts' knowledge to address this research question. Four baseflow separation methods were adopted to derive the long-term monthly baseflow. We then compared the baseflow against field-based EFN and found that different ranges of baseflow can represent field-based EFN. Specifically, 86%-159%, 93%-151%, and 128%-139% of monthly baseflow can be used as EFN standards for snow-melting, summer, and fall-winter, respectively. Further, we found that 102%-150% of the monthly baseflow should be maintained, implying that the presumptive standard underestimated EFN in our study region. Finally, we recommended that baseflow can be an effective index for EFN; however, watershed management should recognize local aquatic conditions in applying the baseflow EFN index for conjunctive watershed management.

Investigating river health across mountain to urban transitions using Pythagorean fuzzy cloud technique under uncertain environment

River health assessment (RHA) is a robust methodology for ascertaining the health of riverine ecosystems, and offering solutions for river conservation and management. Currently, RHA studies have been conducted mainly in mountainous and urban areas, while investigations across mountain to urban transitions remain scarce and insufficient attention has been paid to RHA under uncertain environments. To systematically investigate the RHA across mountain to urban transitions, this study proposed Pythagorean fuzzy cloud (PFC) via integrating the cloud model and Pythagorean fuzzy sets. TOPSIS (Technique for order of preference by similarity to ideal solution) was expanded to the PFC environment to developed a novel PFC-TOPSIS model. The hybrid framework was then created to handle RHA with uncertainty, and the Pi River in China served as a case study. Results showed that the developed models broadened the capabilities of current techniques, and offered a more efficient way for dealing with RHA with uncertainty. In Pi River, the health status showed considerable spatial heterogeneity. Upper reaches were markedly healthier than the lower reaches. Evaluation indicators were at unsatisfactory health levels, with only 68.75% and 18.75% healthy attainment rates in the upper and lower reaches of Pi River, respectively. Meanwhile, 68.75% of the sampling sites were subhealthy and 31.25% were unhealthy. Our research emphasizes that urban development, agricultural practices and dam construction have affected river health in some areas, and appropriate measures are needed to reduce their impacts in Pi River.

The Domestic Considerations of Indian Foreign Policy: A Case Study of Indo-Bangladesh Teesta Water Deal during UPA-II Government

The foreign policy of a country is shaped and influenced not only by the necessity of international environment but also by imperatives of domestic structures and processes. The focus area of the study is primarily Indo-Bangladesh Teesta water deal during UPA-II government. Teesta basin is confronted with a wide range of challenges covering economics, government, and politics to culture, the environment to gender issues to security issues to the health of riverine ecosystems. These concerns, while differing in degree and type, are all tied together by the Teesta, which functions as a common thread flowing through them all and connects them all together. Even though the basin is best known for the lack of a bilateral agreement between India and Bangladesh over water sharing, internal disputes such as the anti-dam motion in Sikkim and the 'Save the Buri Teesta' movement in Bangladesh are also big concerns tied to bilateral trade between the two riparian countries. The study concentrated on the geopolitics of water conflicts in the Teesta basin as well as the role that the TMC party as a domestic factor has played in water negotiations in recent years. The concern of the paper is to examine how a internal domestic considerations of a country act in shaping a country’s foreign policy.

The use of wetted perimeter as habitat proxy to assess environmental flows in Southern Quebec rivers (Canada)

Environmental flows assessment in eastern Canada, and particularly in the province of Quebec, is mainly based on hydrological assessment of historical data during low flow periods. The mean 7-day low flow with return periods of two (7Q2) and ten years (7Q10) are two flow metrics currently used by the Quebec Department of Environment and Fight against Climate Change to prescribe minimum flow and/or maximum water abstraction while maintaining the functions and health of riverine ecosystems. This study investigated the use of the wetted perimeter as an additional environmental flows assessment method. This tool can be used by water managers to maintain the availability of river habitats during low flow periods. Twenty flow metrics were computed for inter-annual, summer and winter periods, for 43 sites from 35 rivers, and analysed to study the changes in wetted perimeter with flow. In addition, the flow associated with maximum curvature (breakpoint) of the flow-wetted perimeter function (QMC) was analyzed. Results provided a better understanding of local changes of river hydraulics and possible aquatic habitat availability associated with different flow metrics. The relevance of using a wetted perimeter threshold (WPSQMC) combined with flow thresholds (Tennant method) was also discussed. The two “fair” Tennant flow thresholds, apart from the twenty flow metrics, would provide sufficient available habitat all year long with corresponding WPSQMC thresholds of 88% and 95% of the 43 river sites. The median discharge for August flow metric for summer and the median discharge for the month with the lowest flow metric value for winter (usually February), provided the highest wetted perimeter in relative terms (72% and 79% respectively of the river sites) compared to the WPSQMC threshold. Using the 7Q2 flow metric would mean maintaining sufficient available habitat for 50%, 60% and 72% of the river sites for respectively inter-annual, summer and winter periods. Considering the single WPSQMC threshold, its associated flow provided the highest values for 16% of the river sites and the second highest one for 9% of the river sites with a single seasonal flow metric value high enough for summer or winter. This study showed that the wetted perimeter is a tool providing additional information on both river morphology and changes in potential aquatic habitat as a function of flow for river sites with small catchment size and low mean annual flow values. Indeed, the wetted perimeter can be very useful in the overall assessment of environmental flows.

Exploring microbiome from sediments of River Ganga using a metagenomic approach

Abstract The Ganga is a major riverine system of India providing ecosystem services to millions of households. However, this river is under stress due to various anthropogenic activities. River sediment harbours a variety of microorganisms which has a tremendous influence on river health. In the present study, metagenomic approach for microbial community characterization of three sediment samples collected from River Ganga at Farakka stretch was carried out. The sediment samples were sequenced using a high-throughput Next Generation Sequencing platform. Taxonomical classification study showed that the occurrence of bacteria is higher than other groups of microbes. The bacterial classes, such as Betaproteobacteria, Deltaproteobacteria, Gammaproteobacteria, and archaeal phylum, Thaumarchaeota, and Crenarchaeota were relatively higher than other communities. KEGG pathway analysis of three samples revealed that the number of genes associated with environmental information processing is higher in the Lalbag sample in comparison to Farakka barrage and Dhulian samples. The microbial community was categorized by functional classification using SEED analysis. Both COG and SEED analysis revealed that genes associated with carbohydrate metabolism are higher than other functional categories. The genus-level study confirms the higher occurrence of Pseudomonas, which corresponds to anthropogenic activities like mass bathing. The presence of bacterial genus Nitrospira and archaeal phylum Thaumarchaeota confirms a healthy nitrogen cycle in the environment. Moreover, the generated information would help in understanding the importance of microbial communities and their imperative function in maintaining the riverine ecosystem health.

Fish size spectra are affected by nutrient concentration and relative abundance of non-native species across streams of the NE Iberian Peninsula

Aquatic ecosystems are strongly body-size structured with a decline of numerical abundance with increasing body size (hereafter, the size spectrum). Marine and lake fish studies have reported consistent variations of size spectra in relation to environmental conditions and biotic composition, but little is known about stream fishes. Accordingly, in this study we test several hypotheses about the effects of local water conditions, biotic introductions and cumulative pressures (measured as the IMPRESS index) on the fish size-spectrum slope (that is, the linear rate of decline of fish abundance as body size increase in a log-log scale) and the size-spectrum intercept (commonly used as proxy for carrying capacity) among 118 local fish assemblages in streams of the NE Iberian Peninsula. To our knowledge, this is the first time that an extensive river fish dataset is used in a dendritic network to cover systematic changes of size-spectrum parameters. We find that the slope and intercept of the fish size spectrum are negatively correlated with nutrient concentration (mainly total phosphorus), with a greater relative abundance of small fishes but a decline of overall carrying capacity. Moreover, fish assemblages with greater relative abundance of non-native species have flatter size-spectrum slopes. In contrast, the IMPRESS index and climate-related variables are poor predictors of the shape of the fish size spectra. This study contributes to better understanding of the main factors structuring fish assemblages in lotic environments of the Iberian Peninsula. We encourage more research on this line to further explore the use of fish size structure to evaluate the ecological health of riverine ecosystems.

Identifying gaps in protected areas to expand integrated riverine ecosystem conservation

AbstractAs demand for water in the arid southwest increases, pressure is mounting on many aquatic and riparian species that rely on riverine habitat for survival. Some of these riverine areas are managed as private, state, or federal lands with differing levels of mandated protections; however, few efforts have explored the potential of filling gaps in riverine protection afforded by designation under the protection of the Wild and Scenic Rivers Act (WSRA) of 1968. Here, we examine how inclusion of eligible rivers, specifically the Nationwide Rivers Inventory (NRI), could fill gaps in protection for a species of high conservation need. A gap analysis overlapping the predicted species range with human disturbances and the level of protection identifies where sufficient protections for a species exist and where there are shortcomings, that is, gaps, potentially addressed by elevating NRI reaches to WSRA protection. This study uses the narrow‐headed garter snake as an indicator species for riverine ecosystem health of free‐flowing perennial reaches within the Arizona/New Mexico Mountains EPA Level III ecoregion. Over a quarter of NRI‐eligible reaches within the ecoregion are within the protection gap for the narrow‐headed garter snake. If designated Wild and Scenic, these reaches could offer needed protection for this species.

A standardised analytical framework for sampling fish communities: relevance to Turkish riverine ecosystems

Fish communities are important indicators of the health of riverine ecosystems. Fish monitoring for The Living Murray (TLM) initiative, one of Australia’s most ambitious restoration undertakings for the degraded river-floodplain biota of the River Murray system (south-eastern Australia), was carried out annually from 2005 to 2011 across six ‘Icon Sites’, including the habitats and reaches therein. These spatial and temporal components of variation in fish community abundance and composition must be taken explicitly into account for consistent assessment of riverine ecosystem health. To address this requirement, a standardised analytical framework, consisting of a sampling design and appropriate statistical methods, is outlined in this study. Based on an extensive dataset, multivariate patterns and univariate trends in fish community structure were analysed to show the flexibility, modularity and ability of the framework. The applicability of the framework to Turkish riverine ecosystems is then discussed with emphasis on the need for participatory discussion between researchers and environmental managers. The possibility to incorporate other measures of fish health such as biomass and condition, and to extend the proposed framework to the quantitative assessment of vegetation and bird communities also exists.

Disentangling Variability in Riverbank Macrolitter Observations.

Anthropogenic macrolitter (>0.5 cm) in rivers is of increasing concern. It has been found to have an adverse effect on riverine ecosystem health, and the livelihoods of the communities depending on and living next to these ecosystems. Yet, little is known on how macrolitter reaches and propagates through these ecosystems. A better understanding of macrolitter transport dynamics is key in developing effective reduction, preventive, and cleanup measures. In this study, we analyzed a novel dataset of citizen science riverbank macrolitter observations in the Dutch Rhine–Meuse delta, spanning two years of observations on over 200 unique locations, with the litter categorized into 111 item categories according to the river-OSPAR protocol. With the use of regression models, we analyzed how much of the variation in the observations can be explained by hydrometeorology, observer bias, and location, and how much can instead be explained by temporal trends and seasonality. The results show that observation bias is very low, with only a few exceptions, in contrast with the total variance in the observations. Additionally, the models show that precipitation, wind speed, and river flow are all important explanatory variables in litter abundance variability. However, the total number of items that can significantly be explained by the regression models is 19% and only six item categories display an R2 above 0.4. This suggests that a very substantial part of the variability in macrolitter abundance is a product of chance, caused by unaccounted (and often fundamentally unknowable) stochastic processes, rather than being driven by the deterministic processes studied in our analyses. The implications of these findings are that for modeling macrolitter movement through rivers effectively, a probabilistic approach and a strong uncertainty analysis are fundamental. In turn, point observations of macrolitter need to be planned to capture short-term variability.

Contributions of suspended load from Missouri River tributaries, southeast South Dakota, and northeast Nebraska: Building a sediment budget

AbstractSuspended sediment plays a critical role in riverine ecosystem health and river processes and is respondent to human alterations such as dams and increased land use. Gavins Point Dam, located on the Missouri River near Yankton, South Dakota, restricts upstream suspended load; yet, suspended sediment concentrations (SSC) increase when the river reaches Sioux City, Iowa. We determined the suspended load concentrations of seven tributaries of the Missouri River entering downstream of the dam. These data were collected from 2012 to 2019 during the summer months of May–July using a depth‐integrated sampler. Sediment rating curves were created based on discharge and SSC. We constructed a simple sediment budget, which indicated that the tributaries located in South Dakota contribute the bulk of the Missouri River's suspended load at ~80%, while the Nebraska tributaries contribute &lt;5%. The remaining sediment is likely supplied by bank and bed erosion. Temporal changes were examined by comparing our recent measurements with historical data from USGS gaging stations on the James River and the Big Sioux River. Suspended sediment and discharge have increased by nearly an order of magnitude, potentially due to increases in precipitation and land use. Sediment budgets are useful resources for informing river management plans on a basin‐wide scale. Given the drastic, long‐term impacts of disruptions to sediment and flow regimes from dams and climate change, this research provides necessary groundwork for remediation efforts and river management.

Sustainability of global Golden Inland Waterways

Sustainable inland waterways should meet the needs of navigation without compromising the health of riverine ecosystems. Here we propose a hierarchical model to describe sustainable development of the Golden Inland Waterways (GIWs) which are characterized by great bearing capacity and transport need. Based on datasets from 66 large rivers (basin area > 100,000 km2) worldwide, we identify 34 GIWs, mostly distributed in Asia, Europe, North America, and South America, typically following a three-stage development path from the initial, through to the developing and on to the developed stage. For most GIWs, the exploitation ratio, defined as the ratio of actual to idealized bearing capacity, should be less than 80% due to ecological considerations. Combined with the indices of regional development, GIWs exploitation, and riverine ecosystem, we reveal the global diversity and evolution of GIWs’ sustainability from 2015 to 2050, which highlights the importance of river-specific strategies for waterway exploitation worldwide.

Phytoplankton assemblage with relation to water quality in Turag River of Bangladesh

The study was performed to evaluate phytoplankton assemblage, physical and chemical characteristics of water, interrelationship between phytoplankton assemblage and physical/chemical characteristics of water and to evaluate water quality index during November, 2015 - September, 2016 for Turag River that is located on the north-eastern side of Dhaka city, Bangladesh. Water samples were collected during winter (November - January/2015-2016), summer (March-May/2016) and rainy season (July September/2016). During the study, the overall phytoplankton assemblage exhibited the following pattern: Bascillariophyceae (40.33%) > Chlorophyceae (32.90%) > Euglenophyceae (14.56%) > Cyanophyceae (12.20%). Fragillaria crotonensis, Navicula grimmei, Phacus circulatus, Euglena agilis, Chlorococcus minutum and Trachelomonas goossensii were dominant phytoplankton species. The average values of water temperature, total dissolved solids (TDS), electric conductivity (EC), pH, dissolved oxygen (DO), biological oxygen demand (BOD5), total nitrogen (TN) and dissolved phosphorus (DP) were 25.94°C, 273.46 mg L-1, 489.71µS cm-1, 6.81, 2.89 mg L-1, 3.85 mg L-1, 8.55 mg L-1 and 0.62 mg L-1, respectively. Euglenophyceae displayed significant negative correlation with DO in winter while TDS in rainy season. Chlorophyceae exhibited significant negative correlation with DP in rainy season. Shannon-Weaver’s (H') and Simpson’s (D) diversity indices ranged between 2.58-3.01 and 0.91-0.95, respectively. In summer, the value of H' (3.01) indicated slight pollution. In winter and rainy seasons, the values of H' were 2.58 and 2.98, respectively displaying light pollution in Turag river. Measured water quality index (WQI) values were 229.71, 171.23 and 74.18 in winter, summer and rainy season, respectively exhibiting that water was unsuitable for drinking purposes in winter and summer and also very poor water quality in rainy season, respectively. The implication of these findings can be used to monitor health of riverine ecosystems which provide ecosystem services for society.

Modeling Benthic Versus Hyporheic Nutrient Uptake in Unshaded Streams With Varying Substrates

AbstractAssessments of riverine ecosystem health and water quality require knowledge of how headwater streams transport and transform nutrients. Estimates of nutrient demand at the watershed scale are commonly inferred from reach‐scale solute injections, which are typically reported as uptake velocities (vf). Multiple interacting processes control vf, making it challenging to predict how vf responds to physical changes in the stream. In this study, we link vf to a continuous time random walk model to quantify how vf is controlled by in‐stream (velocity, dispersion, and benthic reaction) and hyporheic processes (exchange rate, residence times, and hyporheic reaction). We fit the model to conservative (NaCl) and nitrate (NO3−‐N) pulse tracer injections in unshaded replicate streams at the Notre Dame Linked Experimental Ecosystem Facility, which differed only in substrate size and distribution. Experiments were conducted over the first 25 days of biofilm colonization to examine how the interaction between substrate type and biofilm growth influenced modeled processes and vf. Model fits of benthic reaction rates were ∼8× greater than hyporheic reaction rates for all experiments and did not vary with substrate type or over time. High benthic reactivity was associated with filamentous green algae coverage on the streambed, which dominated total algal biomass. Finally, vf was most sensitive to benthic reaction rate and stream velocity, and sensitivity varied with stream conditions due to its nonlinear dependence on all modeled processes. Together, these results demonstrate how reach‐scale nutrient demand reflects the relative contributions of biotic and abiotic processes in the benthic layer and the hyporheic zone.

Coupled effects of land use pattern and hydrological regime on composition and diversity of riverine eukaryotic community in a coastal watershed of Southeast China

The coupled effects of land use pattern and hydrological regime on composition and diversity of riverine eukaryotic community are needed for understanding riverine ecosystem health and algal blooming mechanism. In-situ monitoring and 18S rRNA gene sequencing were used to investigate spatiotemporal variations of eukaryotic community in three types of watershed with different dominant land use type (i.e. urban, forest, and natural) during three seasons (i.e. dry, transition, and wet seasons) in a coastal watershed of Southeast China. Results showed that agricultural and urban watersheds had significantly higher diversity in dry and transition seasons, and higher richness in transition and wet seasons than those in forest watershed. The non-metric multidimensional scaling analysis further verified great spatiotemporal variations of eukaryotic community. Stramenopiles, Alveolata, Animalia, and Eukaryota, dominated the sequences reads for all sampling sites in three seasons. Agricultural watershed had the highest relative abundant of Animalia, whereas Eukaryota was the most abundant in urban watershed and forest watershed had the highest relative abundance of Stramenopiles and Alveolata. The RDA ordination showed that Builtup and streamflow were two most important factors for moderate taxa and abundant taxa, respectively. Variation partitioning revealed that land use pattern and hydrological regime together explained 54.4%, 61% and 67.2% variances of the composition of eukaryotic community. Among three sampling seasons, the relative contribution of land use pattern was higher than that of hydrological regime. The results of this investigation demonstrated how land use pattern and hydrological regime affected the composition and diversity of riverine eukaryotic community. The findings can provide a useful insight into the riverine eukaryotic communities and their underlying ecological mechanisms in coastal China watersheds.

Teleconnection between low flows and large-scale climate indices in Texas River basins

Understanding low flow variability is critical for assessing water quality and health of riverine ecosystems in a river basin. Low flows are dependent on human water abstraction as well as the climate variability. This paper investigates the changing nature of low flows and their association with large-scale climate variability for different watersheds in the State of Texas, USA. For this purpose, we employed trend, wavelet analysis and linear as well as nonlinear correlations to identify important changes in low flow characteristics for three stream-gauging stations selected from different (i.e. Brazos, Colorado and Trinity) river basins located in Texas for the time period of 1916–1959 and 1960–2003. We also investigated the teleconnections between low flow variables and the large-scale climate indices (NINO 3.4, SOI and PDO) using cross wavelet analysis as well as their linear and non-linear correlation relationship. Our results indicated that the low flow magnitudes have shown considerable different characteristics for selected river basins during two separate time periods (1916–1959 and 1960–2003). Based on cross wavelet analysis, we identified that the low flows in selected stations of Colorado and Trinity River basins are likely to be influenced by all three large-scale climate indices. In addition to that, we identified that low flows are more nonlinearly associated with climate indices. Among the selected River basins, the stronger association between low flows and large scale climate indices are observed for Trinity River basin. The results from this study can help in better understanding of low flow hydrology and their potential relationship with large scale indices.

A spatial evaluation of global wildfire-water risks to human and natural systems

The large mediatic coverage of recent massive wildfires across the world has emphasized the vulnerability of freshwater resources. The extensive hydrogeomorphic effects from a wildfire can impair the ability of watersheds to provide safe drinking water to downstream communities and high-quality water to maintain riverine ecosystem health. Safeguarding water use for human activities and ecosystems is required for sustainable development; however, no global assessment of wildfire impacts on water supply is currently available. Here, we provide the first global evaluation of wildfire risks to water security, in the form of a spatially explicit index. We adapted the Driving forces-Pressure-State-Impact-Response risk analysis framework to select a comprehensive set of indicators of fire activity and water availability, which we then aggregated to a single index of wildfire-water risk using a simple additive weighted model. Our results show that water security in many regions of the world is potentially vulnerable, regardless of socio-economic status. However, in developing countries, a critical component of the risk is the lack of socio-economic capability to respond to disasters. Our work highlights the importance of addressing wildfire-induced risks in the development of water security policies; the geographic differences in the components of the overall risk could help adapting those policies to different regional contexts.

Predictability and selection of hydrologic metrics in riverine ecohydrology

AbstractThe natural flow regime is critical to the health of riverine ecosystems. Many hydrologic metrics (HMs) have been developed to describe natural flow regimes, quantify flow alteration, and provide the hydrologic foundation for the development of environmental flow standards. Many applications require the use of models to predict expected natural values of HMs from basin characteristics at sites with no observed records of unimpaired flows. However, the error associated with HM estimation has not been evaluated. The primary goal of our study was to provide guidance for river scientists and managers in the selection, use, and interpretation of HMs for stream classification and hydroecological investigations of river ecosystems. We evaluated the predictability of a broad suite of HMs for the conterminous USA based on random forest statistical models. We also examined how the predictability of metrics varied among unique components of the flow regime. Roughly 40% of 612 HMs we examined could be predict...