Historical Water Research Articles

Monitoring and evaluation of the water quality of the Lower Neches River, Texas, USA

Increasing bacteria levels in the Lower Neches River caused by Hurricane Harvey has been of a serious concern. This study is to analyze the historical water sampling measurements and real-time water quality data collected with wireless sensors to monitor and evaluate water quality under different hydrological and hydraulic conditions. The statistical and Pearson correlation analysis on historical water samples determines that alkalinity, chloride, hardness, conductivity, and pH are highly correlated, and they decrease with increasing flow rate due to dilution. The flow rate has positive correlations with Escherichia coli, total suspended solids, and turbidity, which demonstrates that runoff is one of the causes of the elevated bacteria and sediment loadings in the river. The correlation between E. coli and turbidity indicates that turbidity greater than 45 nephelometric turbidity units in the Neches River can serve as a proxy for E. coli to indicate the bacterial outbreak. A series of statistical tools and an innovative two-layer data smoothing filter are developed to detect outliers, fill missing values, and filter spikes of the sensor measurements. The correlation analysis on the sensor data illustrates that the elevated sediment/bacteria/algae in the river is either caused by the first flush rain and heavy rain events in December to March or practices of land use and land cover. Therefore, utilizing sensor measurements along with rainfall and discharge data is recommended to monitor and evaluate water quality, then in turn to provide early alerts on water resources management decisions.

Reviewing Historic Urban Water Transitions to Advance Water-Sensitive Urban Design for Bhuj, India

In rapidly growing urban contexts, water plays a pivotal role in the transitions the urban environment goes through to sustain the quality of life of its population. Spatial planning and design are essential for the facilitation and manifestation of such transitions. Focusing on Bhuj, a rapidly growing Indian city in a hot arid desert climate, its crucial yet changing sensitivity to urban water flows over time is assessed. The concept of water sensitivity is coined as a goal to pursue by the Water-Sensitive Urban Design approach. In India, however, much of the urban design and development processes are of an unplanned and informal nature, seemingly inhibiting the water sensitivity of urban transitions. Reviewing spatial planning paradigms and their manifestation in space in Bhuj over time, however, brings to light a pre-existing water sensitivity. Yet it also shows a shift from the supply security-oriented ingenious watershed expansion to catastrophe-steered and urban expansion-driven water system negligence. Review and discussion of past and present urban water transitions and management points out drivers, barriers, and their interrelationships, to enable and advance water-sensitive urban development tied to local history, traditional knowledge, and context specificities.

Residential water and energy consumption prediction at hourly resolution based on a hybrid machine learning approach

Predicting water and energy consumption at high resolution over a short-term horizon is critical for water and energy resource management. Water and energy are shown to be closely interlinked in household consumption. However, hourly predictions are often based only on historical consumption data for the resource being predicted, with activity or appliance information and household attribution as additional information. Few studies have used aggregated water and energy consumption for predictions. Within this context, the current study proposed a novel hybrid machine learning model based on the Prophet time-series model, Gated Recurrent Unit network, and self-adaptive weights, called the Prophet-GRU model, which could jointly include historical water and electricity consumption as inputs for hourly water or electricity prediction. Data on hourly water and electricity consumption in six households in Beijing during January–March 2020 were used to train and validate the Prophet-GRU model. The goodness of fit indicator (R2) and prediction accuracy (mean squared error and mean absolute error) for the water and electricity predictions were evaluated. Compared with the single input of water or electricity, with the combined input of data of these two resources, the proposed Prophet-GRU model achieved improvements of 29.2 % and 48.5 % in R2, for water and electricity consumption prediction, respectively. Our results could help better understand water-energy linkages and promote collaborative water and energy management practices.

Water color from Sentinel-2 MSI data for monitoring large rivers: Yangtze and Danube

ABSTRACT Rivers provide key ecosystem services that are inherently engineered and optimized to meet the strategic and economic needs of countries around the world. However, limited water quality records of a full river continuum hindered the understanding of how river systems response to the multiple stressors acting on them. This study highlights the use of Sentinel-2 Multi-Spectral Imager (MSI) data to monitor changes in water color in two optically complex river systems: the Yangtze and Danube using the Forel-Ule Index (FUI). FUI divides water color into 21 classes from dark blue to yellowish brown stemming from the historical Forel-Ule water color scale and has been promoted as a useful indicator showing water turbidity variations in water bodies. The results revealed contrasting water color patterns in the two rivers on both spatial and seasonal scales. Spatially, the FUI of the Yangtze River gradually increased from the upper reaches to the lower reaches, while the FUI of the Danube River declined in the lower reaches, which is possibly due to the sediment sink effect of the Iron Gate Dams. The regional FUI peaks and valleys observed in the two river systems have also been shown to be related to the dams and hydropower stations along them. Seasonally, the variations of FUI in both systems can be attributed to climate seasonality, especially precipitation in the basin and the water level. Moreover, land cover within the river basin was possibly a significant determinant of water color, as higher levels of vegetation in the Danube basin were associated with lower FUI values, whereas higher FUI values and lower levels of vegetation were observed in the Yangtze system. This study furthers our knowledge of using Sentinel-2 MSI to monitor and understand the spatial-temporal variations of river systems and highlights the capabilities of the FUI in an optically complex environment.

75 years of Canada-US transborder water quantity hydropolitics

This paper reviews the history and evolution of Canada-United States transboundary water quantity politics (hydroelectricity, canals, irrigation, etc.) over the last 75 years: megaprojects on the St. Lawrence, Niagara, and Columbia Rivers during the early Cold War, a wide variety of transborder water issues stretching from coast to coast during the latter half of the twentieth century, and then recent hydropolitics concerning diversions from the Great Lakes basin. Utilizing an environmental history approach, and drawing from other fields such as historical geography, water policy, and political ecology, I show that Canada and the United States cooperatively manipulated border water environments on a large scale. Despite this coordination, there was often significant political and diplomatic controversy. I argue that coordinating or dealing with the United States deeply influenced the development of hydroelectricity in Canada, as well as the related hydraulic engineering expertise and technology. Moreover, transborder water politics also influenced many aspects of Canadian economic and political development, including federal-provincial relations. I explore themes such as Canada as a hydro state, the role of the Boundary Waters Treaty and the International Joint Commission, and concepts such as hydraulic nationalism and hydraulic imperialism.

Key perceptions associated with attitudes towards water reuse in a Swedish town

Abstract As climate change and urbanization affect current water management systems, new solutions and approaches rooted in public acceptance are needed to ensure future water supply. In this study, we examine public attitudes to reuse of recycled water and associated worldviews, values, and perceptions in a site without historical water issues. A survey of 143 randomly sampled residents in the municipality of the growing Swedish town Knivsta revealed that 81.4% of the respondents had a positive attitude towards using recycled water in general. The results did not indicate any differences in attitudes between those living in and outside the municipality's urban areas. Perceived benefits and risks were found to be significantly related to both attitudes towards using recycled water in general and to the extreme case of using it for drinking purposes. Additionally, trust in public authorities was highly predictive of attitudes towards drinking recycled water. Furthermore, attitudes were found to be related to an environmental worldview and underlying biospheric, altruistic, and hedonic values. This indicates a need to consider the intended purpose as well as engaging with underlying values as part of the technology legitimation process for improving the chances of successful implementation of water recycling technologies.

A deep learning model for reconstructing centenary water storage changes in the Yangtze River Basin

Since 2002, the Gravity Recovery and Climate Experiment (GRACE) and its Follow-On mission (GRACE-FO) have facilitated highly accurate observations of changes in total water storage anomalies (TWSA). However, limited observations of TWSA derived from GRACE in the Yangtze River Basin (YRB) have hindered our understanding of its long-term variability. In this paper, we present a deep learning model called RecNet to reconstruct the climate-driven TWSA in the YRB from 1923 to 2022. The RecNet model is trained on precipitation, temperature, and GRACE observations with a weighted mean square error (WMSE) loss function. The performance of the RecNet model is validated and compared against GRACE data, water budget estimates, hydrological models, drought indices, and existing reconstruction datasets. The results indicate that the RecNet model can successfully reconstruct historical water storage changes, surpassing the performance of previous studies. In addition, the reconstructed datasets are utilized to assess the frequency of extreme hydrological conditions and their teleconnections with major climate patterns, including the El Niño-Southern Oscillation, Indian Ocean Dipole, Pacific Decadal Oscillation, and North Atlantic Oscillation. Independent component analysis is employed to investigate individual climate patterns' unique or combined influence on TWSA. We show that the YRB exhibits a notable vulnerability to extreme events, characterized by a recurrent occurrence of diverse extreme dry/wet conditions throughout the past century. Wavelet coherence analysis reveals significant coherence between the climate patterns and TWSA across the entire basin. The reconstructed datasets provide valuable information for studying long-term climate variability and projecting future droughts and floods in the YRB, which can inform effective water resource management and climate change adaptation strategies.

Influence of Denitrification on Cyanobacterial Blooms Trends in Lake Taihu, China

Denitrification is a major process in aquatic ecosystems, and it competes with cyanobacterial growth for nitrogen. However, the effect of denitrification on cyanobacterial blooms under the background of climate change remains unclear. This study explored the interaction between lake denitrification and formation of cyanobacterial blooms, using the historical water quality monitoring data of North Lake Taihu over five years from 2017 to 2021 and via incubation experiments of cyanobacteria and sediment denitrification. The monitoring data showed that algal biomass (Chla as a proxy) primarily peaked during summer and autumn. The seasonal variations in total N concentration showed a completely opposite trend than that of algal biomass, which peaked in winter and spring. Nitrate was the major component of dissolved inorganic nitrogen, and the nitrate concentration was approximately zero in summer and autumn. The total phosphorus concentration varied in the same way as the Chla concentration. The experimental results showed that Cyanobacteria did not grow when the temperature was below 20℃. In comparison, denitrification showed a significant linear relationship with temperatures between 10-25℃ (R2=0.99) and reached the maximum value of (62.98±21.36) μmol·(kg·h)-1 in Lake Taihu at 25℃. Additionally, the nitrate concentration threshold at the maximum denitrification rate was 4 mg·L-1. Cyanobacteria assimilate nitrate for growth, thereby reducing the concentration of nitrate required for denitrification. This study indicated that the advance in lake temperature warming due to climate change may result in earlier growth of cyanobacteria, thereby leading to large amounts of N being assimilated by algae before denitrification, further affecting the dynamics of cyanobacterial blooms. The present results are scientifically important for explaining the mechanism of cyanobacterial bloom rebound in Lake Taihu under the background of recent climate changes.

Developing a stochastic hydrological model for informing lake water level drawdown management

Winter drawdown (WD) is a common lake management tool for multiple purposes such as flood control, aquatic vegetation reduction, and lake infrastructure maintenance. To minimize adverse impacts to a lake’s ecosystem, regulatory agencies may provide managers with general guidelines for drawdown and refill timing, drawdown magnitude, and outflow limitations. However, there is significant uncertainty associated with the potential to meet management targets due to variability in lake characteristics and hydrometeorology of each lake’s basin, making the use of modeling tools a necessity. In this context, we developed a hydrological modeling framework for lake water level drawdown management (HMF-Lake) and evaluated it at 15 Massachusetts lakes where WDs have been applied over multiple years for vegetation control. HMF-Lake is based on the daily lake water balance, with inflows simulated by a lumped rainfall-runoff model (Cemaneige-GR4J) and outflow rate calculated by a modified Target Storage and Release Based Method (TSRB). The model showed a satisfactory performance of simulating historical water levels (0.53 ≤ NSE ≤ 0.86), however, uncertainties from meteorological inputs and TSRB determined lake outflow rate affected the result accuracy. To account for these uncertainties, the model was executed stochastically to assess the ability of study lakes to follow the Massachusetts’ general WD guidelines: drawdown by Dec 1 and fully refilled by Apr 1. By using the stochastic HMF-Lake, the probabilities of each lake to reach the drawdown level by Dec 1 were calculated for different drawdown magnitudes (1–6 ft). The probability results suggest it was generally less possible for most of study lakes to achieve a drawdown of 3 ft or more by Dec 1. Moreover, we employed the stochastic model to derive the annual latest refill starting dates that ensure a 95 % probability of reaching the normal water level by Apr 1. We found starting a refill in March for drawdowns up to 6 ft was feasible for most of study lakes. These results provide lake managers with a quantitative understanding of the lake’s ability to follow the state guidelines. The model may be used to systematically evaluate current WD management strategies at state or regional scales and support adaptive WD management under changing climates.

THE EFFECT OF HARBOR DEVELOPMENTS ON HIGH-TIDE FLOODING IN MIAMI (FL)

We develop and validate a tidal-inference based methodology that leverages estimates of historical tidal ranges to obtain historical tidal predictions and constituents. Next, the method is applied to a case study in Miami (Florida), where mean tidal range has more than doubled since 1900, from 0.32 m to 0.66 m today. Water level predictions that represent historical and modern water level variations are projected forward in time using different sea level rise (SLR) scenarios, to see how the historical increase in tidal range affects the occurrence of present-day and future high-tide flooding. To this end, we apply the method of Li et al., (2021), which implies to remove tidal oscillations from present-day water levels and replace them with constant tidal prediction, obtained with tidal constituents representing historic conditions. This creates a synthetic time series that approximates what water levels would have been, had tides not evolved. Possible future water levels are estimated for each SLR scenario for (a) a “tide-only” scenario, using tidal oscillation on top of SLR and accounting for average seasonal cycle of mean sea level (MSL); and (b) a “total water level” approach that includes SLR, non-tidal fluctuations and seasonal sea level. While the first approach neglects relevant forcing (e.g., inter-annual to decadal MSL variability, river discharge, storm surge), it enables us to isolate the contribution of tides to HTF and provides useful metrics for quantifying the effects that tides and SLR have on coastal flooding.

Long-term changes in major ion chemistry-similarities and differences between inflow rivers and the lake in Taihu watershed, China.

The major ion chemistry in the Taihu watershed has dramatically changed due to human disturbances; however, little is known about the similarities and differences in the responses of the inflow rivers and Taihu lake to the disturbances. Using historical (1950s-1970s) and recent (2018-2021) water chemistry data of inflow rivers and the lake, as well as socioeconomic and land use data, we explored the drivers for the major ion chemistry change and different responses of the inflow rivers and the receiving lake. The results indicated that, compared with 1950s-1970s, all the major ions and TDS in rivers and Taihu lake significantly increased (by 91% for Mg2+ and by 395% for Cl- in rivers; by 68% for HCO3- and 134% for Na+ in the lake); however, their increases in major ion composition presented a clear difference, i.e., although current dominant cation remained Ca in inflow rivers, the second dominant cation has shifted from Mg2+ (1950s-1970s) to Na+ (2018-2021) for rivers, while for the lake, the second dominant cation has become frequently Na+ (2018-2021), followed by Ca2+, indicating a clear salinization tendency. Furthermore, the change of some indicative ratio indices of inflow rivers and the lake in the past decades presented an apparent difference, i.e., the river systems had a higher increase rate in Ca2+/Mg2+ and SO42-/Cl- than the lake, while the lake had a higher increase in (Ca2+ + Mg2+)/HCO3-, TH/TA, and Cl-/Na+ than the river systems. Analyses indicated that increased human disturbances were the major driver for the similar increase in the TDS and major ions for both river systems and the lake, while the different algal biomass in the rivers and lake, the land use change, and declined hydrological connectivity in this watershed played important roles in the different alterations of the water chemistry indices. Comparison of major ion correlation change between the running and stagnant waters indicated a clear "lacunification" trend of inflow rivers in terms of water chemistry characteristics in this dense river-network region. Our work revealed the cause and effect of the fundamental water chemistry change in a rapid development region and will provide scientific basis for the integrated management and recovery in the watershed.

Reconstruction of long-term high-resolution lake variability: Algorithm improvement and applications in China

Temporal monitoring of inland water bodies using remote sensing images is often impeded by missing data caused by clouds and other adverse conditions. To date, various data recovery algorithms have been developed based on the water occurrence threshold (WOT), where the contaminated pixels are recovered by using long-term historical water distribution information. Here, we propose an improved algorithm, enhanced WOT (EWOT), which addresses the issue of mismatch between the water occurrence product and the actual historical water presence that has been neglected by previous WOT algorithms. The EWOT algorithm achieved an overall high accuracy (with a mean absolute percentage error (MAPE) = 5.1%) and prevailed against a representative WOT algorithm. The accuracy could be further reduced (MAPE = 1.6%) after the application of a novel quality control process. In addition, the temporal coverage of the high-quality surface water area time series was improved by an average of 26.2%, and the percent count and percent area of lakes with high-quality reconstructed data reached as high as 84.5% and 94.7%, respectively, facilitating the utilization of these data in further time series analysis. In general, the improvement was closely associated with the extent of the contamination before recovery. We evaluated the algorithm's ability to be implemented on a large scale in China, and the results generally were in line with previous studies. Nonetheless, our high-quality annual-based dataset presented a more comprehensive and continuous representation of the changes in lake area spanning from 2000 to 2019. The significance of improving the existing WOT algorithms is highlighted in this study, and the proposed method can be readily extended to lakes worldwide, thus providing a valuable data source to examine the causes and possible impacts of lake dynamics.

Real-Time Control Operation Method of Water Diversion Project Based on River Diversion Disturbance

Changes in water diversion flow are the major disturbance sources in the daily operation of water diversion projects. Ensuring efficient and safe project operation while dealing with different degrees of water diversion disturbance is crucial for real-time control operation. Based on the historical water diversion projects in China and abroad, this study constructs the water diversion disturbance conditions, selects the typical disturbance lines, and constructs the control objectives for different water diversion disturbance lines. The discrete state space equation of the multi-channel pool integral time-delay model is introduced and used as the system prediction model. Concurrently, the simulation results of the river channel hydrodynamic model are used to correct the system state. The model predictive control algorithm is established according to the objective functions of different typical water distribution disturbance lines, and the control strategy of the control gate and pump station along the water diversion project is formulated to assist in the decision making of the project scheduling operation scheme. The proposed method can better cope with different degrees of river diversion disturbance, compensate for the loss of control performance caused by the low accuracy of the generalized model simulation, and improve water level control and sluice regulation.

An Assessment of the Toxicity of Pesticide Mixtures in Periphyton from Agricultural Streams to the Mayfly Neocloeon triangulifer.

Residual concentrations of pesticides are commonly found outside the intended area of application in Ontario's surface waters. Periphyton are a vital dietary component for grazing organisms in aquatic ecosystems but can also accumulate substantial levels of pesticides from the surrounding water. Consequently, grazing aquatic organisms are likely subjected to pesticide exposure through the consumption of pesticide-contaminated periphyton. The objectives of the present study were to determine if pesticides partition into periphyton in riverine environments across southern Ontario and, if so, to determine the toxicity of pesticides in periphyton when fed to the grazing mayfly Neocloeon triangulifer. Sites with low, medium, and high pesticide exposure based on historic water quality monitoring data were selected to incorporate a pesticide exposure gradient into the study design. Artificial substrate samplers were utilized to colonize periphyton in situ, which were then analyzed for the presence of approximately 500 pesticides. The results demonstrate that periphyton are capable of accumulating pesticides in agricultural streams. A novel 7-day toxicity test method was created to investigate the effects of pesticides partitioned into periphyton when fed to N. triangulifer. Periphyton collected from the field sites were fed to N. triangulifer and survival and biomass production recorded. Survival and biomass production significantly decreased when fed periphyton colonized in streams with catchments dominated by agricultural land use (p < 0.05). However, the relationship between pesticide concentration and survival or biomass production was not consistent. Using field-colonized periphyton allowed us to assess the dietary toxicity of environmentally relevant concentrations of pesticide mixtures; however, nutrition and taxonomic composition of the periphyton may vary between sites. Environ Toxicol Chem 2023;42:2143-2157. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Salinity spatial patterns in Mediterranean coastal areas: The legacy of historical water infrastructures

Mediterranean coastal areas have been occupied and developed intensively for a long time facing issues related to agricultural production, urbanization, tourism, preservation of natural resources often linked to salinity. This article explores the relationship between historical land planning and water management, and current soil and water salinity to gain insights into future projections.Soil samples (1185) were collected in a coastal plain of 114 km2 in the south of France and saturated paste extract Electrical Conductivity (ECsp) was deduced from 1:5 dilution. Soil salinity exhibits a wide range of variation (from 0.54 to 113.1 mS cm−1) and spatial patterns. ECsp is significantly different among soil types, higher at depth than at the surface and influenced by the distance to ancient water infrastructures (Pettitt test). Surface water and shallow groundwater samples were collected for trace element concentrations and Oxygen (18O/16O) isotope ratio measurements. The geochemical signatures indicate a mixture between surface freshwater and seawater, reveal the presence of over-salted seawater and a stratification of salinity from the surface to the depth.Results suggest that groundwater is the source of soil salinity, and illustrate the long-term impact of old water infrastructures. Less saline soils are found near the freshwater supply channel (constructed from 15th to 18th), while more saline soils are located near drainage channels. The presence of over-salted water reflects temporal evolution of the plain over the last few centuries (initially under seawater, gradually filled in, presence of ponds and salt works that have now disappeared). The current soil salinity patches continue to be a visible reminder of this evolution. The trend towards desalinization of the plain over the last few centuries has been made possible by massive freshwater inflows, which are now under threat due to the general decrease of water resources availability.

Stories of a water-table: anomalous depressions, aquitard breaches and seasonal implications, Shelby County, Tennessee, USA

An extensive water level survey of the water-table aquifer (i.e., shallow aquifer) within Shelby County, Tennessee, was conducted in the dry (fall 2020) and wet (spring 2021) seasons. Water-table surfaces were generated using cokriging to observe seasonal differences to identify anomalous water-table depressions, indicative of an underlying aquitard breach. Seasonal differences were attributed to non-coincident control and timing between the surveys and when optimum dry (fall) and wet (spring) conditions existed, as observed through comparisons with continuous historical water levels from 12 shallow monitoring wells. Additionally, data from fall 2020 were compared to previous studies in 2005 and 2015 to determine decadal changes in levels and shape of the water-table surface which were mostly attributed to changes in data control and potential climate variations. A prediction error map was generated from the 2020 dataset to identify areas of the county with high-prediction error (>7.0 m) to offer guidance on where future well control would be optimal.

Optimizing Solution in Decision Supporting System for River Basin Management Consisting of a Reservoir System

Decision support systems tackle problems and require systematic planning. They consider physical data, hydrological data, and sediment levels to achieve efficiency and adaptability in various situations. Therefore, this research aims to identify alternative engineering choices for the management of a river basin with a single reservoir system. Optimization techniques, including marine predator algorithm (MPA), genetic algorithm (GA), genetic programming (GP), tabu search (TS), and flower pollination algorithm (FPA), were applied to find the optimal reservoir rule curves using a reservoir simulation model. The study focused on the Ubolratana Reservoir in Thailand’s Khon Kaen Province, considering historic inflow data, water demand, hydrologic and physical data, and sedimentation volume. Four scenarios were considered: normal water scarcity, high water scarcity, normal excess water, and high excess water. The optimal rule curves derived from the reservoir simulation model, incorporating sedimentation and hedging rule (HR) criteria, were found to be the best engineering choices. In the normal and high water scarcity scenarios, they minimized the average water shortage to 95.558 MCM/year, with the lowest maximum water shortage 693.000 MCM/year. Similarly, in the normal and high excess water scenarios, the optimal rule curves minimized the average excess water, resulting in a minimum overflow of 1087.810 MCM/year and the lowest maximum overflow 4105.660 MCM/year. These findings highlight the effectiveness of integrating optimization techniques and a reservoir simulation model to obtain the optimal rule curves. By considering sedimentation and incorporating HR criteria, the selected engineering alternatives demonstrated their ability to minimize water shortage and excess water. This contributes to improved water resource management and decision-making in situations of scarcity and excess.

Short-term legacy effects of long-term nitrogen and water addition on soil chemical properties and micro-bial characteristics in a temperate grassland.

Nitrogen deposition and summer precipitation in eastern Inner Mongolia are predicted to increase in recent decades. However, such increases in nitrogen inputs and precipitation may not be continuous under the future new patterns of global change, with the direction and magnitude of which may change or weaken. The legacy effects of nitrogen and water addition after cessation on ecosystems are still unclear. Based on a 13-year nitrogen and water addition experiment in temperate grassland of northern China, we examined the short-term (2 years) legacy effects of historical nitrogen and water addition on soil physicochemical properties and microbial properties after the cessation of nitrogen and water addition in the 14th year. The results showed that the positive effects of historical nitrogen addition on most of soil nutrient variables diminished after two years of cessation, including ammonium nitrogen, nitrate nitrogen, dissolved organic carbon and nitrogen, and Olsen-P concentrations. In contrast, there were legacy effects on soil microbial characteristics. For example, the historical nitrogen input of 15 g N·m-2·a-1 reduced microbial biomass carbon, respiration, and alkaline phosphomonoesterase activity by 73.3%, 81.9%, and 70.3% respectively. It implied that microbial parameters restored slowly in comparison with soil nutrients, showing a hysteresis effect. Results of Pearson's correlation and redundancy analysis showed that the legacy effects of historical nitrogen addition on microbial parameters could be attributed to the negative effects of nitrogen addition on soil pH. Historical water addition showed significant legacy effects on soil pH, ammonium nitrogen, dissolved organic carbon and nitrogen, respiration, and soil enzyme activities, which significantly interacted with historical nitrogen addition. These results are of great significance to predict the changes in grassland ecosystem functions and services under the local environmental improvement conditions, and to reveal the restoration mechanism of degraded grassland.

Ohio City Replaces Historic Water Treatment Plant

Ohio City Replaces Historic Water Treatment Plant

Estimates of Sudan’s historical water withdrawals from the Nile

Lacking reliable information on water withdrawals in the Nile Basin poses a major challenge for efficient water management. The annual amount of water withdrawn from the Nile in Sudan has been a notable research gap, with implications for various aspects. In the current research, we employed three methods to estimate the historical water withdrawals of Sudan from the Nile. These methods are based on (i) closing water balance by using river discharge and evaporation losses from surface water bodies, (ii) estimating incremental evapotranspiration through satellite information, and (iii) accounting for water needed for domestically-produced agricultural commodities. The results indicate that Sudan's water withdrawal from the Nile has increased substantially over the last decades. The highest magnitude of water withdrawal was observed during the last decade (2011–2020). Depending on the method used, this estimate ranged, on average, between 16.0 ± 2.2 km3 and 17.8 ± 1.3 km3. Given Sudan’s ambitious plans to expand the irrigated croplands horizontally, this upward trend in water withdrawal is likely to continue. To cope with the expected limitation in water resources, Sudan should adopt a vertical development pathway in the agricultural sector that prioritizes enhancing water use efficiency and improving crop productivity. The current research findings have immediate and far-reaching implications for the mode of development in the water and agriculture sectors in the country and transboundary water management.