Zero-flow Days Research Articles

Perennial and Non‐Perennial Streamflow Regime Shifts Across California, USA

AbstractDespite rises in drought frequency and human water demands, streamflow regime shifts from perennial to non‐perennial have not been evaluated in many arid/semi‐arid regions. To document shifts, we created a methodology that classifies streams as naturally perennial or non‐perennial. Our classification used historical, minimally disturbed‐quality USGS streamflow gages (1950–2015) across California. The number of consecutive zero flow days (≥5 days) was used to classify 61% (96/158) and 39% (62/158) of gages as perennial and non‐perennial, respectively. We developed a random forest model to predict flow regime class based on climate and watershed characteristics. To identify regime shifts, we compared the observed class of contemporary (1980–2023) minimally disturbed and disturbed gages with their modeled, natural class. For most minimally disturbed gages, the observed and natural predicted classes were the same, but 13% (7/52) of gages had a modeled perennial regime with an observed non‐perennial class, indicating a drying trend. Among disturbed gages, 22% (64/290) shifted from perennial to non‐perennial and 7% (21/290) from non‐perennial to perennial. Trends in the minimum 7‐day moving average and number of zero‐flow days provided further evidence of drying at minimally disturbed streams, but no pattern at disturbed gages. Our results indicate that few minimally disturbed perennial streams have become non‐perennial to date, but many streams have experienced drying from climate. Streams impacted by human activities had greater drying rates, but regulation has caused some non‐perennial streams to become perennial. By quantifying expected natural streamflow regimes, this work can help monitor, manage, and conserve stream ecosystems.

Assessment of Climate Change Effects of Drought Conditions Using the Soil and Water Assessment Tool

A combination of annual peak water demand due to seasonal population spikes along with small and shallow aquifers has prompted an assessment of the region’s watersheds as operating at a net water deficit. This study uses the Soil and Water Assessment Tool (SWAT) to simulate historical drought conditions in the Chipuxet watershed in Rhode Island, USA. The calibrated and validated model uses the Soil Moisture Deficit Index (SMDI) and Evapotranspiration Deficit Index (ETDI) as well as an Indicators of Hydrological Alteration (IHA) calculation to determine the frequency and severity of historical droughts and to simulate climate change conditions developed through a downscaled climate model selection. The output data for the historical and climate change scenarios were analyzed for drought frequency and severity. Results indicate that water stress will increase in both low-emission (RCP4.5) and high-emission (RCP8.5) scenarios. Additionally, the SMDI and ETDI show that RCP8.5 climate scenarios will have more severe deficits. Finally, IHA data indicate that zero-flow days and low-flow durations increase under all climate scenarios.

Hydrologic changes in the Brazos River Basin and implications for Great Plains fishes

Alteration of natural flow regimes from surface water and groundwater resource development has adversely impacted aquatic habitats of resident fish throughout the Great Plains. Two endangered cyprinids, Sharpnose Shiner Notropis oxyrhynchus and Smalleye Shiner N.buccula, were historically found throughout the Brazos River Basin in Texas. However, their range has been greatly reduced by construction of impoundments and stream depletion from groundwater pumping. Successful recruitment requires flowing, unobstructed river reaches of sufficient velocity to suspend semi-buoyant fertilized fish ova. The wide, shallow stream habitats the shiners utilize are now limited to the Upper Brazos River Basin upstream of Possum Kingdom Reservoir. This study assesses the relative importance of long-term climate variability, reservoir construction, and groundwater development on Upper Brazos streamflow regimes by (1) calculating flow metrics (2) evaluating groundwater-surface water interactions and long-term groundwater inflows, and (3) using mixed-effects regression models and Poisson regression. Results show that fish habitat has been threatened through several impacted hydrologic processes: (1)groundwater development has resulted in reduced mean daily flows, peak flows, and zero-flow days, (2)upstream impoundments have increased zero-flow days and reduced mean daily flows, and (3)lower mean daily flows and peak flows now occur during droughts, suggesting water resource development—particularly after 1970—has exacerbated drought effects. We illustrate this approach using the Upper Brazos River Basin; however, the methodology applied can inform management actions to maintain spawning flows for streams in similar altered basins.

Climatic and anthropogenic drivers of zero-flow events in intermittent rivers in Poland

River intermittence was studied based on data from hydrological monitoring in Poland. We screened the entire state database and two another data sources applying the criterion for zero-flow event: discharge less than 0.0005 m 3∙s –1, and found five intermittent rivers with catchment area from 9.2 to 303.7 km 2. We aimed at finding associations between intermittence and climatic driving forces (temperature and precipitation), and between intermittence and anthropogenic activity. We used the Spearman correlation coefficient, circular statistics, and statistical tests for trend. The concentration of zero-flow days, mostly in summer, and the decreasing trend in the standardised precipitation evapotranspiration index ( SPEI) in all catchments at various aggregation levels, and an increasing trend in the total number of zero-flow days and in the maximum length of zero flow events in two rivers, were detected. The strong negative correlation (–0.62 ≤ ρ < 0) between intermittence and the SPEI backward lagged in time showed that intermittence resulted from prolonged deficits in climatic water balance due to increasing evapotranspiration. The reaction of the Noteć catchment, amplified by the anthropogenic pressure (brown coal mines), was reflected in the atypical shape of the rose diagram and in inhomogeneities in river discharges. The results show that the rose diagram can serve as an indicator of the degree of anthropogenic impact on runoff conditions.

Featured Collection Introduction: National Water Model III

Featured Collection Introduction: National Water Model III

Classification and Prediction of Natural Streamflow Regimes in Arid Regions of the USA

Understanding how natural variation in flow regimes influences stream ecosystem structure and function is critical to the development of effective stream management policies. Spatial variation in flow regimes among streams is reasonably well understood for streams in mesic regions, but a more robust characterization of flow regimes in arid regions is needed, especially to support biological monitoring and assessment programs. In this paper, we used long-term (41 years) records of mean daily streamflow from 287 stream reaches in the arid and semi-arid western USA to develop and compare several alternative flow-regime classifications. We also evaluated how accurately we could predict the flow-regime classes of ungauged reaches. Over the 41-year record examined (water years 1972–2013), the gauged reaches varied continuously from always having flow > zero to seldom having flow. We predicted ephemeral and perennial reaches with less error than reaches with an intermediate number of zero-flow days or years. We illustrate application of our approach by predicting the flow-regime classes at ungauged reaches in Arizona, USA. Maps based on these predictions were generally consistent with qualitative expectations of how flow regimes vary spatially across Arizona. These results represent a promising step toward more effective assessment and management of streams in arid regions.

Modeling alterations in flow regimes under changing climate in a Mediterranean watershed: An analysis of ecologically-relevant hydrological indicators

The potential response of flow regimes to future climate has crucial importance for a variety of practical applications, such as sustainable water management and ecological asset preservation. For this study, multi-site investigations of alterations in flow regimes under projected climate change were performed for one of the largest watersheds in Morocco, the Bouregreg Watershed (BW). Future daily streamflow was simulated using the eco-hydrological model Soil and Water Assessment Tool (SWAT) forced by climatic data from CMIP5 model outputs. Simulations were carried out for two periods: 2035–2050 (2040s), and 2085–2100 (2090s) under two emissions scenarios: RCP4.5 and RCP8.5. Future streamflow regimes were examined in accordance with an Indicators of Hydrologic Alteration (IHA) analysis, while being confronted with baseline flow data. Mean temperature has been predicted to increase by up to 2.79 °C in the 2090s (RCP8.5), and a higher variability in rainfall regime is expected. The results indicate that, under future changes in climate patterns, flow regimes in BW will be altered. However, the extent of alteration will be reflected unevenly among the four streams of the study watershed. The IHA analysis revealed that most of the river network will experience both a decrease in monthly flow magnitude (mostly in November and December), and an increase (dominantly in February and March) when compared to baseline. The frequency of flash pulses, and the number of zero-flow days are also expected to increase. Most of the projected alterations were estimated to become very significant in the 2090s under the RCP8.5 scenario. The potential ecological implications were also analysed, and the most sensitive streams of BW were identified to guide local water planning and ecological preservation strategies.

Hydrological changes along the Jing River and its causal analysis

The hydrological response of rivers to upstream reservoir regulation is one of the increasingly important research issues of watershed management. In this study, a hydrodynamic coupling model was used to simulate water level and flow processes of the Jing river and diversion flow of three outlets before and after the operation of TGP (Three Gorges Projects). The results indicated that water level and flow of three diversion channels both decreased in flood and dry seasons: the compensation regulation of the TGP was significant to maintain the water level and flow of three diversion outlets in the Jing river, but it also increased zero-flow days in the diversion channels of the Yangtze River. The riverbed erosion of channels in the upper reaches as well as lower reaches caused hydraulic gradient varying so much that it can’t be ignored in the water exchange process between the Yangtze and Jing river. This mechanism cooperates with the operation of TGP to change the natural process of the Yangtze-Jing river’s hydrologic process. This work provides essential information for future water resources and environmental management of the river-lake system and facilitates the effective flow regulation of dams, which has significant implications not only for the Dongting river-lake system but also the similar lakes and rivers elsewhere.

Trends in flow intermittence for European rivers

ABSTRACT Intermittent rivers are prevalent in many countries across Europe, but little is known about the temporal evolution of intermittence and its relationship with climate variability. Trend analysis of the annual and seasonal number of zero-flow days, the maximum duration of dry spells and the mean date of the zero-flow events is performed on a database of 452 rivers with varying degrees of intermittence between 1970 and 2010. The relationships between flow intermittence and climate are investigated using the standardized precipitation evapotranspiration index (SPEI) and climate indices describing large-scale atmospheric circulation. The results indicate a strong spatial variability of the seasonal patterns of intermittence and the annual and seasonal number of zero-flow days, highlighting the controls exerted by local catchment properties. Most of the detected trends indicate an increasing number of zero-flow days, which also tend to occur earlier in the year, particularly in southern Europe. The SPEI is found to be strongly related to the annual and seasonal zero-flow day occurrence in more than half of the stations for different accumulation times between 12 and 24 months. Conversely, there is a weaker dependence of river intermittence with large-scale circulation indices. Overall, these results suggest increased water stress in intermittent rivers that may affect their biota and biochemistry and also reduce available water resources.

Impacts of coal mining and coal seam gas extraction on groundwater and surface water

This paper presents an assessment of the hydrological impacts of proposed coal mines and coal seam gas (CSG) developments in the Gloucester, Hunter, Namoi and Galilee subregions of eastern Australia. Surface water and groundwater modelling was carried out to assess the cumulative regional-scale hydrological impacts of multiple coal and coal seam gas developments. The hydrological metrics assessed were groundwater drawdown and changes in low-flow characteristics as measured by the number of low-flow or zero flow days per year. Uncertainty in the modelling was also considered, and the results are presented as the median and plausible range (5th to 95th percentile) from many simulations which attempt to capture a wide range of uncertainty. The results indicate that under the best-case (5th percentile) scenario, the impact of additional/proposed coal resource developments on groundwater drawdown and surface water characteristics can be quite small. However, under the worse-case (95th percentile), groundwater drawdown is very likely for up to 5 km from the coal resource developments, but unlikely beyond 20 km. Altered surface water characteristics can extend for many kilometres downstream, particularly in unregulated systems. The cumulative hydrological impact is enhanced where there are multiple developments in close proximity. The results are being used to inform policy and the approval process for coal resource developments.

Enhanced low flow prediction for water and environmental management

The ability to predict low river flows is critical to water resources planning to sustain a healthy river ecosystem. However, the estimation of reliable low flows is difficult for a variety of reasons including lack of its proper conceptualisation. Consequently, arbitrary flow data transformation is done to enhance the influence of lower flows to help improve the goodness-of-fit during parameter optimisation in rainfall-runoff modelling. We carried out systematic model calibration using a range of flow data transformations to identify the one that results in best goodness-of-fits in 595 catchments across different rainfall regions of Australia. Effects of transformation methods on the prediction of low flow surrogates, namely the Baseflow Index (BFI) and cease-to-flow days or the Zero Flow Days (ZFD) were also investigated and regionalised. We found that the square-root transformation performed the best in modelling flow time series in all rainfall regions of Australia and for different ranges of precipitation and forest cover. Model parameters from most flow transformations predicted the mean annual ZFD and mean annual BFI well. Parameters from the log- and reciprocal-transformed flow were best in estimating the annual ZFD, while square-root and no-transformation did well in predicting the annual BFI. The observed BFI and ZFD were strongly correlated with the mean annual precipitation at a 5% significance level in all regions. It is also the biggest influencing factor for ZFD and BFI among several catchment attributes. ZFD and BFI had a strong negative correlation with each other implying that they may be interchangeable as low flow surrogates. There was a clear and widespread reduction in the probability of baseflow occurrence during the Australian millennium droughts of 2001–2010. The probabilities were reduced by up to 70% compared to the before-drought baseflow probability.

Linking the recruitment and survivorship of a freshwater stream-specialist fish species to flow metrics in Mediterranean climate temporary streams

ABSTRACTNovel modelling was utilised in the present study to reveal significant relationships between the abundance of the Australian freshwater stream-specialist fish Galaxias olidus and metrics defining flow regimes across a region dominated by temporary streams. It was revealed that increases in total abundance were linked to metrics (both 1- and 3-year periods) that indicate greater water availability and the persistence of water in pools across the year, namely the average duration of zero-flow days over the low-flow season (negatively) and total duration of bankfull flows across the year (positively). The analysis identified 3-year metrics as being more important to the abundance of 0+ fish rather than annual ones. Taken together, these findings describing the flow requirements of a stream specialist will help to guide implementation of environmental flows, but will also highlight the need for continued exploration of flow–ecology relationships.

Ecohydrological Index, Native Fish, and Climate Trends and Relationships in the Kansas River Basin.

This study quantified climatological and hydrological trends and relationships to presence and distribution of two native aquatic species in the Kansas River Basin over the past half-century. Trend analyses were applied to indicators of hydrologic alteration (IHAs) at 34 streamgages over a 50-year period (1962-2012). Results showed a significant negative trend in annual streamflow for 10 of 12 western streamgages (up to -7.65 mm/50 yr) and smaller negative trends for most other streamgages. Significant negative trends in western Basin streamflow were more widespread in summer (12 stations) than winter or spring (6 stations). The negative-trend magnitude and significance decreased from west to east for maximum-flow IHAs. Minimum- flow IHAs, however, significantly decreased at High Plains streamgages but significantly increased at Central Great Plains streamgages. Number of zero-flow days showed positive trends in the High Plains. Most streamgages showed negative trends in low- and high-flow pulse frequency and high-flow pulse duration, and positive trends in low-flow pulse duration. These results were consistent with increasing occurrence of drought. Shift in occurrence from present (1860-1950) to absent (2000-2012) was significantly related (p<0.10) to negative trends of 1-day maximum flows (both species) and indices associated with reduced spawning-season flows for Plains Minnow and shifting annual-flow timing and increased flow intermittency for Common Shiner. Both species were absent for all western Basin sites and had different responses to hydrological index trends at eastern Basin sites. These results demonstrate ecohydrological index changes impact distributions of native fish and suggest target factors for assessment or restoration activities.

Landscape and flow metrics affecting the distribution of a federally-threatened fish: Improving management, model fit, and model transferability

Truncated distributions of pelagophilic fishes have been observed across the Great Plains of North America, with water use and landscape fragmentation implicated as contributing factors. Developing conservation strategies for these species is hindered by the existence of multiple competing flow regime hypotheses related to species persistence. Our primary study objective was to compare the predicted distributions of one pelagophil, the Arkansas River Shiner Notropis girardi, constructed using different flow regime metrics. Further, we investigated different approaches for improving temporal transferability of the species distribution model (SDM). We compared four hypotheses: mean annual flow (a baseline), the 75th percentile of daily flow, the number of zero-flow days, and the number of days above 55th percentile flows, to examine the relative importance of flows during the spawning period. Building on an earlier SDM, we added covariates that quantified wells in each catchment, point source discharges, and non-native species presence to a structured variable framework. We assessed the effects on model transferability and fit by reducing multicollinearity using Spearman’s rank correlations, variance inflation factors, and principal component analysis, as well as altering the regularization coefficient (β) within MaxEnt. The 75th percentile of daily flow was the most important flow metric related to structuring the species distribution. The number of wells and point source discharges were also highly ranked. At the default level of β, model transferability was improved using all methods to reduce collinearity; however, at higher levels of β, the correlation method performed best. Using β=5 provided the best model transferability, while retaining the majority of variables that contributed 95% to the model. This study provides a workflow for improving model transferability and also presents water-management options that may be considered to improve the conservation status of pelagophils.

A spatial assessment of stream-flow characteristics and hydrologic alterations, post dam construction in the Manyame catchment, Zimbabwe

The global hydrologic regime has been intensively altered through activities such as dam construction, water abstraction, and inter-basin transfers. This paper uses the Range of Variability Approach (RVA) and daily stream flow records from nine gauging stations to characterize stream-flow post dam construction in the Manyame catchment, Zimbabwe. We identify which variables continue to be altered, upstream and at different distances downstream, to distinguish sections with the highest potential for ecological disruption and to understand how hydrological alterations dissipate downstream of dams. Our results indicate that different sections of the same river have different stream-flow characteristics post dam construction. The most adverse effects of dams were on downstream stretches of the river which were characterized by low flows, extreme low flows and an increased number of zero-flow days. These differences reflect the operation rules of the Manyame catchment dams. While the change in stream-flow characteristics is apparent in the 0-10 km range, it is slightly felt in the 11-20 km range and totally disappears at distances >20 km downstream of dams. These changes in stream characteristics, and that damming is only restricted to the upper third of the catchment, make the hydrologic fragmentations in the catchment minor. However, the continued hydrologic alterations post dam construction raise important concerns about the interactions of hydrology with other factors like sediment deposition upstream of dams and climate change. We recommend that catchment managers target enhancing the natural flow variability of the river instead of meeting target flows.

Classifying the flow regimes of Mediterranean streams using multivariate analysis

Rivers in the Mediterranean region often exhibit an intermittent character. An understanding and classification of the flow regimes of these rivers is needed, as flow patterns control both physicochemical and biological processes. This paper reports an attempt to classify flow regimes in Mediterranean rivers based on hydrological variables extracted from discharge time series. Long-term discharge records from 60 rivers within the Mediterranean region were analysed in order to classify the streams into different flow regime groups. Hydrological indices (HIs) were derived for each stream and principal component analysis (PCA) and then applied to these indices to identify subsets of HIs describing the major sources of variations, while simultaneously minimizing redundancy. PCA was performed for two groups of streams (perennial and temporary) and for all streams combined. The results show that whereas perennial streams are mainly described by high-flow indices, temporary streams are described by duration, variability and predictability indices. Agglomerative cluster analysis based on HIs identified six groups of rivers classified according to differences in intermittency and variability. A methodology allowing such a classification for ungauged catchments was also tested. Broad-scale catchment characteristics based on digital elevation, climate, soil and land use data were derived for each long-term station where these data were available. By using stepwise multiple regression analysis, statistically significant relationships were fitted, linking the three selected hydrological variables (mean annual number of zero-flow days, predictability and flashiness) to the catchment characteristics. The method provides a means of simplifying the complexity of river systems and is thus useful for river basin management. Copyright © 2015 John Wiley & Sons, Ltd.

Modeled intermittency risk for small streams in the Upper Colorado River Basin under climate change

• We analyzed historic flow records from streams in the Upper Colorado River Basin. • Dry years with high temperatures and low precipitation had more zero-flow days. • Mean flow was positively related to minimum flows. • Important predictors of low flow were: precipitation, PET, soils, drainage area. • Streams with high variability and low flows will be prone to more intermittency. Longer, drier summers projected for arid and semi-arid regions of western North America under climate change are likely to have enormous consequences for water resources and river-dependent ecosystems. Many climate change scenarios for this region involve decreases in mean annual streamflow, late-summer precipitation and late-summer streamflow in the coming decades. Intermittent streams are already common in this region, and it is likely that minimum flows will decrease and some perennial streams will shift to intermittent flow under climate-driven changes in timing and magnitude of precipitation and runoff, combined with increases in temperature. To understand current intermittency among streams and analyze the potential for streams to shift from perennial to intermittent under a warmer climate, we analyzed historic flow records from streams in the Upper Colorado River Basin (UCRB). Approximately two-thirds of 115 gaged stream reaches included in our analysis are currently perennial and the rest have some degree of intermittency. Dry years with combinations of high temperatures and low precipitation were associated with more zero-flow days. Mean annual flow was positively related to minimum flows, suggesting that potential future declines in mean annual flows will correspond with declines in minimum flows. The most important landscape variables for predicting low flow metrics were precipitation, percent snow, potential evapotranspiration, soils, and drainage area. Perennial streams in the UCRB that have high minimum-flow variability and low mean flows are likely to be most susceptible to increasing streamflow intermittency in the future.

Fundamental spatial and temporal disconnections in the hydrology of an intermittent prairie headwater network

Summary We characterize the hydrology of intermittent prairie headwater streams of the Konza Prairie Biological Station (Konza) located in northeastern Kansas, USA. Flow records from four gaging stations were used to quantify flow intermittence and mean and peak annual discharges. Gage sites used in this analysis are classified as harshly intermittent with all sites having over 90 days of zero-flow annually. The largest basin had the fewest zero-flow days and the shortest durations of zero-flow while the smallest basin had the most zero-flow days and the highest frequency zero-flow durations. There were strong correlations between total annual precipitation and the total number of zero-flow days and the number of zero-flow periods. Correlations were less strong between the Palmer Drought Severity Index (PDSI) and the number of zero-flow days and between PDSI and the number of zero-flow periods. Basin-averaged total annual precipitation poorly predicted mean annual and peak annual discharges. Double mass plots of streamflow to precipitation and streamflow in the headwaters to the receiving stream demonstrate many instances of flow desynchronization. Results of this study suggest that local watershed-scale processes, such as groundwater storage in limestone and alluvial strata, dynamic infiltration flow paths, and soil moisture conditions, produce a threshold-driven hydrologic response, decoupling the headwater hydrologic regimes from sub-annual weather patterns.

Fish assemblages in subtropical rivers: low-flow hydrology dominates hydro-ecological relationships

Effective environmental flow management depends on identification of ecologically-relevant flow attributes to maintain or restore flows in the context of other natural and human influences on stream ecosystems. This study in subtropical eastern Australia identified associations of fish with climatic and flow gradients, catchment topography, reach geology, habitat structure and land use across 20 catchments. Land-use patterns and associated stressors accounted for very little variation in fish assemblage structure. Of the 35 fish species analysed, 24 were strongly associated with gradients in mean daily flows and their variability, baseflow, number of zero-flow days and high-flow pulses, magnitude of the 1-year annual return interval flood and the constancy and predictability of monthly flows. The finding that 22 species (benthic and pelagic) were associated with gradients of antecedent low-flow hydrology indicates that these species (or functional trait groups) should be the focus of further analysis to explore hydro-ecological relationships in systems with regulated flow regimes.Editor Z.W. Kundzewicz; Guest editor M. AcremanCitation Arthington, A.H., Rolls, R.J., Sternberg, D., Mackay, S.J., and James, C.S., 2014. Fish assemblages in subtropical rivers: low-flow hydrology dominates hydro-ecological relationships. Hydrological Sciences Journal, 59 (3–4), 594–604.

Analysing changes in water availability to assess environmental water requirements in the Rivirivi River basin, Southern Malawi

The headwater catchments of the Rivirivi River basin in Malawi play a vital role in meeting downstream water requirements. In recent years, the Rivirivi River flow regime has experienced changes in its hydrological regime, including an increased number of zero-flow days. This study was aimed at investigating some of the causes of these changes. Water quantity indicators were assessed through flow duration analysis of the river flow regime behavior before and after the introduction of the traditional water allocation practices and dam construction. Further, a desktop reserve model was applied to estimate the environmental water requirements. Anthropogenic land use induced change patterns were investigated by time series analysis of satellite imagery and their potential effect on water resources were inferred. The results indicate that there was a considerable difference in average annual stream flow between two identified main periods (between 1963–1983 and 1984–2004) and zero flows increased from 5% to 12%. In addition, the area experienced a 65% reduction in forest cover from 1992 to 2008 which resulted in increased high flow index by 16%. Furthermore, the ecosystems need approximately the range of 35–40% of the MAR to be maintained at Class A and the range of 9–13% of MAR for class D. The results suggest that anthropogenic activities have negatively affected low flow environmental flows requirements by increasing zero flow days in Rivirivi River catchment. However, total water usage remains below the river’s MAR and the river can meet all water needs with proper management of the river flow regime.