Low Flow Years Research Articles

Assessing the impact of rainfall on water quality in a coastal urban river utilizing the environmental fluid dynamics code

The Haihe River, flowing through Tianjin City, grapples with pollution challenges, notably high levels of nitrogen (N) and phosphorus (P) leading to eutrophication and unpleasant odors, particularly aggravated by rainfall. This study used Environmental Fluid Dynamics Code to comprehensively analyze the water environment under three scenarios: low flow year, normal flow year, and high flow year. The investigation delves into N and P concentrations, computes atmospheric deposition fluxes, and evaluates the loads and retention ratios of N and P in the urban river network of Tianjin City. Scenario analysis reveals distinct trends, with high flow years associated with elevated N and hydrodynamics levels, while low flow years exhibit contrasting patterns. Key findings include 1) wet deposition fluxes contributing 21% of NH4+-N and 9% of TP river loads, 2) continuous rainfall and runoff resulting in immediate or delayed increases in NH4+-N, TN, and TP concentrations in surface water, 3) an increase in average N:P mole ratios downstream along the Haihe River, and 4) N and P mean retention ratios were 48% and 63%, respectively. The study suggests that implementing sponge city construction and sustainable drainage systems may improve water quality by mitigating the direct discharge of rainfall runoff into the river.

Planning and implementing genetic rescue of an endangered freshwater fish population in a regulated river, where low flow reduces breeding opportunities and may trigger inbreeding depression.

Augmenting depleted genetic diversity can improve the fitness and evolutionary potential of wildlife populations, but developing effective management approaches requires genetically monitored test cases. One such case is the small, isolated and inbred Cotter River population of an endangered Australian freshwater fish, the Macquarie perch Macquaria australasica, which over 3 years (2017-2019) received 71 translocated migrants from a closely related, genetically more diverse population. We used genetic monitoring to test whether immigrants bred, interbred with local fish and augmented population genetic diversity. We also investigated whether levels of river flow affected recruitment, inbreeding depression and juvenile dispersal. Fish length was used to estimate the age, birth year cohort and growth of 524 individuals born between 2016 and 2020 under variable flow conditions. DArT genome-wide genotypes were used to assess individual ancestry, heterozygosity, short-term effective population size and identify parent-offspring and full-sibling families. Of 442 individuals born after translocations commenced, only two (0.45%) were of mixed ancestry; these were half-sibs with one translocated parent in common. Numbers of breeders and genetic diversity for five birth year cohorts of the Cotter River fish were low, especially in low-flow years. Additionally, individuals born in the year of lowest flow evidently suffered from inbreeding depression for juvenile growth. The year of highest flow was associated with the largest number of breeders, lowest inbreeding in the offspring and greatest juvenile dispersal distances. Genetic diversity decreased in the upstream direction, flagging restricted access of breeders to the most upstream breeding sites, exacerbated by low river flow. Our results suggest that the effectiveness of translocations could be increased by focussing on upstream sites and moving more individuals per year; using riverine sources should be considered. Our results indicate that river flow sufficient to facilitate fish movement through the system would increase the number of breeders, promote individuals' growth, reduce inbreeding depression and promote genetic rescue.

Crop Coefficient of Sunflowers under Drip Irrigation with Plastic Film in Different Hydrological Years in the Hetao Irrigation District

An accurate assessment of crop water requirements during the crop growth period can help organize irrigation schedules and investigate the hydrological environments in irrigation districts, especially in shallow groundwater districts. In irrigation scheduling, crop coefficients, representing three development stages, play a critical role in modeling evapotranspiration. Therefore, in this study, the crop coefficient (Kc) of sunflowers under drip irrigation in different hydrological years in the Hetao irrigation district with shallow groundwater is determined. Based on the analysis of rainfall frequency, the experimental situations of 2012, 2013, and 2014 are adopted as high, normal, and low flow years. Using the water balance method, groundwater recharge and crop evapotranspiration in different hydrological years were investigated. The results showed that the groundwater recharge in a high-flow year was larger than that in normal and low-flow years with values of 67.47, 66.75, and 42.61 mm, respectively. Crop evapotranspiration is directly related to the irrigation amount at the same growth stage. The Kc of sunflowers in a high-flow year is higher by 0.1 and 0.15 than that in normal and low-flow years. The Kc of sunflowers under drip irrigation is lower than that under surface irrigation by 8.9% in the initial and late stages of sunflower growth, but higher than that by 10.6% in the mid-stage, which is due to differences in small water potential differences and less evapotranspiration in the initial and late stages under drip irrigation. The study is of great significance for formulating a reasonable schedule of drip irrigation with shallow groundwater and improving the field environment.

Hyporheic Oxygen Dynamics in the East River, Colorado: Insights From an In‐Situ, High Frequency Time Series During Two Distinct Flow Seasons

AbstractDissolved oxygen (DO) is critical for aquatic ecosystems, however, few studies have focused on the long‐term DO dynamics in hyporheic zones, which are a function of both transport (hydrologic exchange between river and hyporheic zone) and uptake by biogeochemical reactions or respiration. We explore the dynamics of temperature and DO at 10, 20, and 35 cm depth beneath the East River, Colorado, from July–October 2017 (relatively normal water year) and April to October 2018 (comparatively low flow year), enabled by distinctive, in‐situ, high frequency (Δt = 5 min) sensors that provided continuous time‐series from the undisturbed study site over 14 months. We expect that hyporheic DO, which has a regular daily fluctuation pattern, is supplied by the surface water (at all times we estimate downwelling) and that diurnal hyporheic DO temporal patterns should be aligned with diurnal hyporheic temperature patterns. However, this was not found to be the case. Hyporheic DO becomes depleted briefly at 20 and 35 cm depths in 2017, and at all three hyporheic depths for extended periods in 2018. Whereas diurnal temperature fluctuations have consistent timings of maxima and minima, hyporheic DO rarely has as regular a pattern, and daily ranges are inconsistent. Rainfall events caused some of these changes to diurnal hyporheic DO patterns without repeatable effects. Antecedent snowpack conditions influence streamflow dynamics and therefore hyporheic DO dynamics in this alpine river. These results also point to the strong and variable influence of hyporheic microbial communities regulating hyporheic DO.

Human activities have more impacts on the recent discharge reduction of the largest tributary of the Yellow River relative to last three centuries

How to quantitatively decouple the impacts of climate change and human activities on river discharge changes is a challenge in current global change research. As the largest tributary of the Yellow River (YR), the Weihe River (WR) is a typical river whose discharge is influenced by climate change and human activities. Here, we first attempt to obtain the normal-flow season and high-flow season discharge in the lower reaches of the WR by using tree rings and historical documents, respectively. The relationship between natural discharge in the two seasons is unstable and complex since 1678. Using an innovative method, we reconstructed the natural discharge from March to October (DM-O), which explains >73 % of the variance in the observed DM-O during the modeling period 1935–1970. There were 44 high-flow years, 6 extremely high-flow years, 48 low-flow years and 8 extremely low-flow years from 1678 to 2008. The contribution of WR annual discharge to the YR is 17 % over the past three centuries, and their natural discharge changes synchronously rise and fall. Human activities, such as the construction of reservoirs and check-dams, agricultural irrigation and domestic and industrial water consumption, have more impacts than climate change on the decrease in the observed discharge. In total, 53.5 % of the discharge reduction since 1971 is due to human activities, and 46.5 % is due to climate change. In addition, this study provides an important model for how to quantify the influences of human activities and nature on discharge reduction and to reconstruct seasonal resolution climate in global change studies.

Water resources optimal allocation model for coordinating regional multi-level water resources managers’ interests

In water resources management on a global scale, it is important to reconcile the conflicting interests of different regions and actors regarding water use. To solve this issue more effectively, an optimal allocation model of water resources that coordinates the interests of regional multi-level water resource managers and balances the benefits acquired by regional multi-level water resource managers was proposed. The model consisted of three components, including option generation, option selection, and fallback bargaining. The Hybrid Strategy Whale Optimization Algorithm (HSWOA) was created to generate the initial alternative set throughout the alternative generation process. In the alternative screening process, quick non-dominated sorting was used to choose Pareto alternatives from the initial alternative set. Through many rounds of negotiations, water resource managers at all levels reached a consensual water resource allocation plan during fallback bargaining. This model was used to reconcile the conflicting water interests of municipal and county water managers in Handan, China, in terms of economic, social, and ecological benefits. It was also compared with the Pareto solution set obtained from NSGA-III. In terms of convergence speed and accuracy, the results demonstrated that HSWOA outperformed the Whale Optimization Algorithm (WOA). The results show that several rounds of discussions between municipal and county water management eventually resulted in Nash equilibrium. In normal flow year, the recommended scheme could yield economic benefit of 315.08×108 Yuan, social benefit of 0.1700, and ecological benefit of 5.70 × 106 m3, whereas in low flow year, the recommended scheme could yield economic benefit of 354.85×108 Yuan, social benefit of 0.2103, and ecological benefit of 57.82 × 106 m3. Compared to existing studies, the recommended scheme has clear advantages in terms of social and ecological benefits. The proposed optimal water resource allocation was Pareto optimal. This paper presented a new way of thinking about reconciling the conflicting interests of different levels of water resource managers in the process of water allocation.

Melting Alpine Water Towers Aggravate Downstream Low Flows: A Stress‐Test Storyline Approach

AbstractDroughts can lead to extreme low flow situations in rivers, with resulting severe impacts. Upstream snow and ice melt in many of the world's mountain water towers can alleviate the hydrological consequences of drought, yet global warming threatens the cryosphere. To improve the understanding of melt water contributions during drought in the case of future glacier retreat, we developed stress‐test storyline scenarios to model streamflow and tested them in the European river Rhine basin. Meteorological conditions of past drought and low flow years in Europe, 1976, 2003, and 2018, were repeated at three future moments in time, representing nowadays, near future and far future conditions. The latter two conditions were obtained by climate projections under the RCP8.5 scenario. Results show that the low flow situations caused by the meteorological drought situations aggravate in future conditions, more so for the far future and for the year 2003 because of the relatively large glacier ice melt contribution in the past. Summer (July–September) streamflow may decline by 5%–25% far downstream and 30%–70% upstream and the duration of extreme low flow situations may double compared to the selected past drought events. These results are relevant for the Rhine as a major European river but stand exemplary for many other river basins and highlight the importance of cryospheric changes for downstream low flow situations in a changing climate. The stress‐test scenarios allow a glimpse into future extreme low flow events aiding adaptation planning, and might be adapted to include other important low flow drivers.

Ecological Flow Response Analysis to a Typical Strong Hydrological Alteration River in China.

Ecological flow is an important indicator for reflecting the stability of a watershed ecosystem. The calculation of ecological discharge under hydrological variation has become a research hot-spot. The Ganjiang River south of Poyang Lake in China was taken as an example in this study. Hydrological Alteration Diagnosis System methods were used to detect the change-points. The Distributed Time Variation Gain Model (DTVGM) was used to carry out runoff restoration. The Probability-weighted Flow Duration Curve was applied to calculate the ecological flow. The results showed that: (1) The hydrological alteration of the Waizhou Station occurred in 1991, the annual runoff increased by 10%, and the Gini coefficient (GI) increased by 0.07 after the change-point. The change in precipitation was the main driving factors. (2) The R value and NSE of the DTVGM were greater than 0.84, which represents the feasibility of the model used to restore runoff. (3) Compared to the traditional hydrological method, the proposed method can better reflect the inter-annual difference of ecological flow, flow ranges for high, normal, and low flow years are 398-3771 m3/s, 352-2160 m3/s, and 277-1657 m3/s, respectively. The calculation method of ecological flow in rivers considering hydrological variation can more scientifically reflect the impact of hydrological variation on ecological flow process, ecological flow under different human activities that can be calculated, such as dam control, water intake and water transfer, furthermore, it also provides a scientific basis for water resources planning and allocation under changing environment.

The first tree-ring reconstrruction of streamflow variability over the last ∼250 years in the Lower Danube

Paleoclimate reconstructions are increasingly used to characterize climate variability and change prior to the instrumental record, in order to improve our estimates of climate extremes and to provide a baseline for climate change projections. Most of these reconstructions are focused on temperature, precipitation, and/or drought indices and, to a lesser extent, reconstruct streamflow variability. In this study, the first regional tree-ring width chronology (i.e. Quercus sp.), from the Caraorman forest (Danube Delta, Romania), was used to reconstruct the last ∼250 years of annual (from November previous year to July of the current year) streamflow of the Lower Danube River. The obtained results indicate a stable and significant correlation between the tree-ring width index from the Caraorman forest and the Danube streamflow at the Ceatal Izmail hydrologic station situated in the southeastern part of Europe. Interannual streamflow variation for the analyzed period indicates 14 extremely high flow years, with streamflow greater than 8780 m3/s (1770, 1771, 1799, 1836, 1838, 1839, 1871, 1876, 1877, 1879, 1940, 1941, 1997 and 2010) and 14 extremely low flow years, with streamflow lower than 5300 m3/s (1741, 1745, 1750, 1753, 1773, 1794, 1812, 1832, 1843, 1882, 1899, 1921, 1964 and 1994). Periods characterized by pluvials in the lower Danube Delta are associated with a low-pressure system centered over Europe, positive sea surface temperature (SST) anomalies over the Atlantic Ocean, and negative SST anomalies over the Baltic, North, and Mediterranean Seas. These large-scale conditions favor the advection of moist air from the Mediterranean and the Black Sea towards the southeastern part of Romania, which in turn leads to high precipitation rates over this region. Opposite to this, low streamflow years are associated with a high-pressure system centered over Europe, characterized by a northward shift of the storm tracks and negative SST anomalies over the Atlantic Ocean, and positive SST anomalies over the Baltic, North, and Mediterranean Seas. Based on our results, we argue that the reconstruction of river streamflow data based on the tree-ring width has important scientific and practical implications for a better understanding of the streamflow variation of the past, necessary for water resource management and environmental-hydrological protection.

Distribution of heavy metals influenced by pumped storage hydropower in abandoned mines: Leaching test and modelling simulation

Renewable energy generation varies frequently, making it difficult to match electricity demand. Pumped storage hydropower plants can alleviate this problem by reducing the unevenness of renewable energy generation. It is a new exploration of energy storage methods to construct pumped storage hydropower plants by using underground goaf of abandoned mines and mining subsidence water area. However, the construction of lower reservoirs using underground goaf areas of abandoned mines can lead to potential heavy metal pollution. To assess the impact of using abandoned mines for pumped storage hydropower on the downstream surface water environment, this work first analyzed the release characteristics of heavy metals from underground goaf and surface dump through field sampling and leaching tests, then constructed a water-environment model of the downstream surface water based on the experimental results and water environment theory, and finally simulated and analyzed the impact of underground pollutants pumped to the surface on downstream surface water-quality in typical hydrological years. The maximum error between the simulated values and measured values of the hydrodynamic model was 0.1, and the overall error was within a reasonable range (±0.2 m). The comparison between simulated values and measured values of heavy metal concentration in water quality model showed RMSE values ranged from 0.003 to 0.81, with an average of 0.4; the SI ranged from 0.84 to 0.95, with an average of 0.89. During the simulation of low, normal, and high flow years, pollution downstream was concentrated near the drainage outlet, and the underground pollutants pumped to the surface influenced the concentration of heavy metals there. After a period of drainage, the concentration of heavy metals decreased. Drainage volume was an important factor affecting the concentration of heavy metals downstream surface water. These results prove that the water environment model established based on MIKE21 is reliable and can provide guidance for the simulation and control of heavy metal pollution in the utilization of abandoned mines for pumped storage hydropower. This work provides a reproducible idea and method to assess the impact of using abandoned mines and mining subsidence water area for pumped storage hydropower on downstream surface water and ensure the safety of the ecological environment.

Pre‐instrumental perspectives on Arkansas River cross‐watershed flow variability

AbstractWe present four reconstruction estimates of Arkansas River baseflow and streamflow using a total of 78 tree‐ring chronologies for three streamflow gages, geographically spanning the headwaters in Colorado to near the confluence of the Arkansas‐Mississippi rivers. The estimates represent different seasonal windows, which are dictated by the shared limiting forcing of precipitation on seasonal tree growth and soil moisture—and subsequently on the variability of Arkansas River discharge. Flow extremes that were higher and lower than what has been observed in the instrumental era are recorded in each of the four reconstructions. Years of concurrent, cross‐basin (all sites) low flow appear more frequently during the 20th and 21st Centuries compared to any period since 1600 A.D., however, no significant trend in cross‐basin low flow is observed. As the most downstream major tributary of the Mississippi River, the Arkansas River directly influences flood risk in the Lower Mississippi River Valley. Estimates of extreme high flow in downstream reconstructions coincide with specific years of historic flooding documented in New Orleans, Louisiana, just upstream of the Mississippi River Delta. By deduction, Mississippi River flooding in years of low Arkansas River flow imply exceptional flooding contributions from the Upper Mississippi River catchments.

Response of phytoplankton community composition to physicochemical and meteorological factors under different hydrological conditions in Lake Diefenbaker

Changes in hydro-meteorological conditions due to warming climate and the operation of reservoirs may support algal blooms. Lake Diefenbaker is a large reservoir on the Canadian Prairies. Annual flow volume from its major tributary, the South Saskatchewan River (SSR), varies with precipitation and temperature in the Rocky Mountains. Furthermore, plans are underway to increase water abstraction from Lake Diefenbaker for irrigation. Therefore, we used a nine-year dataset that comprised a drought year (1984), four consecutive high flow years (2011 to 2014), and four subsequent low flow years (2015 to 2018) to investigate how these changes could affect the major phytoplankton groups and cyanobacterial community. Diatoms (38.5%) were the most abundant phytoplankton, followed by cryptomonads (28.9%) under low and high flow years. Diatoms were associated with greater mixing in late spring and fall, whereas the cryptomonads were related to the high nutrients from spring flow. Cyanobacteria (79.3%) contributed the greatest to the total phytoplankton biomass under drought; we hypothesized that the high abundance of cyanobacteria during drought was associated with thermocline deepening and subsequent internal loading of nutrients. Microcystis, a potential bloom-forming and toxin-producing genus, was dominant during the drought and correlated with reduced water level, increased air temperature, and moderate wind speed. Although its biomass was low, another potential bloom-forming and toxin-producing genus, Aphanizomenon, was present in low and high flow years. Aphanizomenon was correlated with decreased SSR flow and increased particulate carbon to particulate phosphorus ratios, which may be related to their ability to cope with P limitation. These results highlight that Lake Diefenbaker and other similar reservoirs are vulnerable to an increase in potential toxic cyanobacteria species with future expectations of climate warming and water abstraction.

Study of Water Resources Optimal Operation Model of Multireservoir: A Case Study of Kuitun River Basin in Northwestern China

Aiming at the problems that need to be solved urgently in the current operation of a multireservoir in Kuitun River Basin, such as the uneven distribution of water resources in time and space, the large workload of manual operation calculation, and low coordination level, the paper takes the optimal operation of water resources in the basin as the main goal and carries out the research on the optimal operation model of the multireservoir in combination with the complex characteristics of local water resources system. Firstly, based on the generalization of hydraulic engineering in Kuitun River Basin, a water resources optimal operation model of the multireservoir is established and is solved by the graph theory. Then, the actual data of typical years were selected to test the model. The test results show that, compared with the actual water distribution, the water shortage rate of 2015 and 2016 in high flow years decreased by 98.57% and 100%, respectively; the water shortage rate of 2013 and 2014 in normal flow years decreased by 92.65% and 96.38%, respectively; and the water shortage rate of 2009 in a low flow year decreased by 87.78%. The model can provide the optimal operation scheme for the optimal operation of the multireservoir in the basin. And it can solve the problems such as the uneven distribution of water resources and the large workload of manual operation calculation and can provide technical support for the optimal operation of water resources of the multireservoir in Kuitun River Basin in the future.

Extreme Low Flows in Rivers of the East European Plain in the 19th–21st Centuries

This study is focused on extreme low flows in rivers (when water flow is less than or equal to 75 and 90% exceedance probability) in the East European Plain (Volga, Don, Dnieper, Western Dvina, and Northern Dvina) in the 19th–21st centuries. It is shown that the proportion of years in which an extreme low flow is observed in one or more seasons of the year or in the year as a whole during the entire observation period varies from 46 to 57%. In 30 years, a low flow formed only in one basin under consideration, and in 50 years, it was observed in several (from 2 to 5) basins simultaneously. In seven years, an extreme low flow was observed in different hydrological seasons and during the entire years simultaneously in all the rivers and, in nine cases, in four basins. Modern global warming leads to a significant decrease in the number of low-flow years in the winter and summer-autumn low-water seasons and the year as a whole for all the rivers under consideration. In years when severe draughts were recorded in the territories of all river basins under consideration, low flows were recorded only in 1921 and 1972.

Basin-Wide Water Resources Management Strategies Improve Cooperation Effectiveness and Benefits

Basin-wide cooperation is an approach to resolve water disputes and improve the resilience of transboundary river basins to extreme droughts under climate change. However, the effectiveness of cooperation among various stakeholders has disputes in moving from theoretical research to practical application. This paper aims at developing basin-wide water resources management strategies to improve cooperation effectiveness in the Lancang-Mekong River Basin (LMB). An interdisciplinary physically based integrated hydroeconomic water system model is developed for strategy evaluation, and is shown to have good performance in reproducing historical events. First of all, we find that agricultural benefits in downstream countries are primarily affected by hydrological conditions, without significant impacts from reservoir construction. Second, the cooperative action—three-phase emergency water supply—by upstream reservoirs discharge can alleviate the agricultural drought of downstream countries, and it is further improved by better spatial and temporal water reallocation among different stakeholders. Last but not least, we characterize the cooperation effectiveness under different hydrological conditions by two indicators (i.e., incremental benefit and cooperation efficiency). They show two opposite trends: from extremely high-flow years to extremely low-flow years, the incremental benefit brought by basin-wide cooperation increases by nearly six times, whereas the cooperation efficiency (measured by how many times benefits are gained by downstream from upstream unit loss) decreases by 80 percent. This study provides guidance and support for transboundary basin cooperation and sustainable management.

Optimization of Ecological Water Replenishment Scheme Based on the Interval Fuzzy Two-Stage Stochastic Programming Method: Boluo Lake National Nature Reserve, Jilin Province, China.

In this paper, a fuzzy mathematical programming method is introduced on the basis of the interval two-stage stochastic programming (ITSP) optimisation model for the wetland ecological water replenishment scheme in Boluo Lake National Nature Reserve. The minimum ecological water supply is taken as the objective function, and the lake bubble water diversion capacity, lake bubble water supply capacity, water diversion sequence, ecological service value, and minimum capacity of the wetland water supply are taken as constraints. The ecological water replenishment schemes of five lakes in the Boluo Lake National Nature Reserve are optimised at the levels of low flow years, normal flow years, and high flow years, and an optimised model for the wetland ecological water replenishment scheme in Boluo Lake National Nature Reserve based on the interval fuzzy two-stage stochastic programming (IFTSP) method is constructed. The model fully considers the waste of water resources and the protection of migratory bird habitat and makes rational allocation of water resources to make full use of flood resources. The IFTSP model proposed herein fully considers the fuzzy and uncertain characteristics of the planning area in the lake bubble area of Boluo Lake National Nature Reserve and improves the decision-making efficiency of decision-makers by providing technical support for smooth implementation of the ecological water replenishment project in nature reserves. The model can also be used as a theoretical guide for ecological recharge projects in other regions of the world.

Streamflow variability in the past four centuries for the largest tributary of the Yellow River and its teleconnection with large‐scale climate forcing

AbstractUnderstanding long‐term hydroclimate change and its evolution mechanism is beneficial to hydrological assessments and future planning in the Weihe River Basin, a region affected by the East Asian monsoon, as well as addressing increasing concerns about water resources due to social and economic development. The average June–July streamflow reconstruction was performed for the period from 1592 to 1988 for the Weihe River, based on the common growth responses relating tree‐ring width, minimum density and hydrological variables, as inferred from the first principal component series of tree‐ring width and density. The statistical results of calibration and verification confirmed that our model was credible and could explain 47.2% of the variance in the calibration period from 1937 to 1970. According to the criteria of one standard deviation less or greater than the mean value, 59 extremely low flow years and 62 high flow years were identified, accounting for 14.86% and 15.62%, respectively, of the past 397‐year hydrological reconstruction. Severe dryness and wetness periods were in good agreement with other hydrological records in the basin, suggesting the coherence of hydroclimate changes at the basin scale, including extreme drought events from the 1920s to 1930s. The reconstructed streamflow had significant interannual and interdecadal periodic signals associated with spatial correlations with sea surface temperatures in the Pacific, Indian and Atlantic Oceans, indicating the relationships between hydrological variations in the Weihe River and the natural forcing related to the El Niño‐Southern Oscillation, Pacific Decadal Oscillation, Indian Ocean Dipole pattern, North Atlantic Oscillation and Atlantic Multidecadal Oscillation (AMO). Our results provide new evidence for the potential of hydrological research using multiple tree‐ring indicators, such as tree‐ring width and minimum density, in the semiarid and semihumid areas of central China.

Integrated Water-Power System Resilience Analysis in a Southeastern Idaho Irrigation District: Minidoka Case Study

This study investigates the joint water–power system resilience of an irrigation district in southeastern Idaho. Irrigation districts face difficulties in the delivery of water to farmers under drought conditions, during equipment failures, or unplanned infrastructure disruptions. The resilience of interconnected water and power systems can be better analyzed and understood through an integrated approach, using a model that connects the dependencies between the two halves of the system. Using a multi-agent system model capturing both water and power system components, as well as their linkages, we capture the interdependencies of these systems and highlight opportunities for improvement when faced with disruptions. Through simulation scenarios, we examine the system resilience using system performance, quantified as the percentage of met demand of the power and water system, when subjected to drought water year, an unforeseen water demand increase, power outage and dam failure. Scenario results indicate that the effects of low flow years are mostly felt in the power system; unexpected increases in water demand marginally impact irrigation system performance; dams and pumps present vulnerabilities of the system, causing substantial unmet demand during disruptions. Noting the interdependencies between the water–power system halves while leveraging an integrated simulation allows for an insightful analysis of the system impacts during disruptions.

Boat-electrofishing transect location and flow levels: influence on riverine fish monitoring in non-wadeable habitats

Fisheries monitoring can be improved by studying the influence of gear selectivity, sampling design, and habitat conditions. We used boat-electrofishing data to investigate how sample unit placement (shoreline and channel transects) and sampling conditions (low and high flow years) affect detection of fishes in a highly regulated Ontario (Canada) river system. Species detection histories associated with a spatially replicated sampling design was fit to a Bayesian hierarchical site occupancy model for 14 fishes. Habitat (transect location) had a significant effect on detection probabilities (p) for all species, with shoreline sampling more likely to detect species than channel. Sampling year had a significant effect on detectability of six species. The relative influence of habitat and sampling year varied among species. Detection probabilities based on combined shoreline and channel transect data across both years ranged from 0.09 to 0.48 and were positively correlated to species abundance. High detection probabilities and precise occupancy estimates were associated with sunfish and bass abundant in shoreline habitats. Small-bodied species closely associated with the riverbed or exhibiting schooling behavior tended to be poorly detected. Power to detect future changes in species distribution is expected to differ based on habitat sampled, with greater power associated with shoreline boat-electrofishing. Detecting small to moderate changes is not likely for most species. The addition of channel transects did not improve the effectiveness of shoreline sampling. Improvements to the current design could be realized by reallocating sampling effort from channel to shoreline and testing different gear in deep (> 3m) habitats.

Numerical Modeling of Soil Water–Heat Transport under Oxo-Biodegradable Film Mulch and the Optimal Mulching Period

Timely monitoring and regulation of the transport and distribution of soil water and heat are appropriate methods to ensure and improve crop yields. With the degradation of the oxo-biodegradable film, the upper boundary condition is a time-variable boundary, and soil water-heat transport is more complicated, comparing with conventional plastic film. Based on HYDRUS-2D version 2.02 and the characteristics of mulching films, a soil water-heat coupled transport mathematical model of drip irrigation was established, and the simulated soil water content and temperature were tested against three-year field observations for calibration and validation purposes. The model prediction demonstrated that the induction periods of oxo-biodegradable film mulching differed in different hydrological years. In normal flow years, an induction period of 50–80 days had higher water use efficiency. While the window would increase to 50–100 days in low flow years. As for temperature, comparing with conventional plastic film mulching, the decreasing trend of temperature started to slow down when the induction period increased to 70 days. Therefore, the optimal induction period of the oxo-biodegradable film is 50–70 days.