Increased River Flow Research Articles

Impacts on the quality of surface water in a urban perimeter of the Rio Grande watershed, Brazilian Cerrado.

The aim of this study was to assess the spatiotemporal variation in water quality in the Grande River and the Ondas River, in the city of Barreiras, Bahia, Brazil. Water samples were collected at 11 points along the rivers, and eight physical-chemical parameters (electrical conductivity, pH, alkalinity, apparent and true color, turbidity, dissolved oxygen, and biochemical oxygen demand) and three microbiological indicators (heterotrophic bacteria, total and thermotolerant coliforms) were analyzed. Spatiotemporal variation was assessed using the multivariate techniques of principal component analysis/factorial analysis (PCA/FA) and hierarchical cluster analysis (HCA). The results of the PCA/FA highlighted eight of the eleven parameters as the main ones responsible for the variations in water quality, with the greatest increase in these parameters being observed in the rainy season, especially among the points influenced by sewage discharges and by the influence of the urban area. The CA grouped the results from 11 points into three main groups: group 1 corresponded to points influenced by sewage discharges; group 2 grouped points with mainly urban influences; and group 3 grouped points in rural areas. These groupings showed the negative influence of urbanization and also statistically significant variations between the groups and periods. The most degraded conditions were in group 1, and the least degraded conditions were in group 3. Assessment of the variations between the monitoring periods showed that rainfall had a significant impact on the increase or decrease in the parameters assessed, as a result of surface runoff linked to urbanization and increased river flow.

River Flashiness in Great Britain: A Spatio-Temporal Analysis

Flashiness refers to the rapidity and frequency of fluctuations in river flow. It can provide insights into flooding, by capturing dramatic increases in river flow, as well as contaminant transport, relating to concentrations of diffuse pollution. Despite a very well gauged river system, there is limited research in Great Britain targeting this component of river flow. This study addresses that gap in knowledge, with a detailed spatio-temporal analysis of river flashiness in Great Britain. Using 513 gauging stations, with historical records of at least 30 years, the average Richards–Baker flashiness index (RBI¯) was calculated for 1990–2020, showing an overall west- (0.6–0.8) to east-coast (0.1–0.2) gradient, being higher in the west (with the exception of some gauges in the south-east). Employing random forest models, the main predictor for flashiness was found to be soil composition, with some additional region-specific predictors. These include flood attenuation by reservoirs and catchment areas, affecting flashiness in the north and west of Great Britain. Additionally, using a subset of 208 gauging stations with data recorded from 1970 to 2020, a temporal analysis examined significant breakpoints and/or trends in yearly flashiness, using the Pettitt test and Mann–Kendall trend test, respectively. Increases in flashiness were found mainly in the north-east and south-west of Great Britain, with implications in flooding and river health. On a seasonal scale, and using a monthly RBI¯, the timing of flashy events was found to oscillate between autumn and spring over the 50 years, gravitating around winter.

Hydrologic Versus Biogeochemical Control of Nutrient Dynamics in a Shallow Hypersaline Coastal Lagoon: Insight From a Coupled Hydrodynamic‐Water Quality Model

AbstractShallow coastal lagoons with restricted connection to the ocean are often productive but can also be sensitive to nutrient enrichment and hydrologic changes. Resolving nutrient dynamics is important for their sustainable management, yet being able to accurately resolve nutrient budgets has remained a challenge due to their complex hydrological regimes and habitat heterogeneity. In this study, we undertake a systematic nutrient budget of a large shallow hypersaline lagoon (Coorong, South Australia), with assistance of a high‐resolution coupled hydrodynamic‐biogeochemical model, to demonstrate the conditions that lead to nutrient retention. Under current conditions, high rates of evapo‐concentration and limited water connectivity have led to a persistent accumulation of nutrients and poor water quality in substantial areas of the lagoon. The interplay between hydrological drivers and biogeochemical processes was quantified using an adjusted Damköhler number, comparing the timescales of nutrient flushing versus processing. This showed a general transition from hydrologic control to biogeochemical control with increasing distance from the main ocean connection, modified by episodes of increased flows and external loads. Whilst water age was a useful indicator of the factors controlling rates of nutrient retention, interannual variability in retention between areas of the lagoon was explained based on river flows and changes in mean sea level. As the system has been affected by reduced flows over past decades, the results provide evidence that increasing river flow to the lagoon would reduce the nutrient retention, and we discuss the potential for net nutrient export to the ocean under sustained high flows.

Seasonal and interannual variations of suspended particulate matter in a West-African lagoon (Nokoué lagoon, Benin): Impact of rivers and wind

This study, based on five years of monthly in situ data collected from 2018 to 2022, examines the seasonal and interannual fluctuations of suspended particulate matter (SPM) concentration in Nokoué Lagoon, Benin. Seasonally, SPM exhibits significant variations primarily influenced by changes in river discharge. During low-flow periods (December to May), SPM concentrations are relatively low (<15 mg L-1) throughout the lagoon. During this time, slight temporal variations are correlated with wind energy and likely associated with wind-induced resuspension of sediments. This is confirmed by slightly higher concentrations of SPM in the bottom layers compared to the surface. Resuspension appears to be lower in the west than in the east, likely due to the increased presence of acadjas (brush parks) in the west, reducing fetch and wind intensity, thus decreasing resuspension. At the onset of the river flood period (July–August), associated with the West African monsoon, increased river flow generates a significant turbid plume extending from the northeast of the lagoon to the Cotonou channel, connecting the lagoon to the Atlantic Ocean. SPM levels then increase considerably (>100 mg L−1), with a pronounced SPM gradient from the western to eastern regions of the lagoon. The less dense freshwater laden with sediment from the rivers flows over the denser saline water of the lagoon, leading to slightly higher SPM concentrations in the surface layers. Between September and November, SPM concentration gradually decreases as river flows reach their peak values. Thus, on a seasonal scale, the relationships between SPM and river discharge show a temporal lag, resulting in a clockwise hysteresis cycle. This is explained by the early mobilization of fine sediments during rising river flows, followed by reduced sediment availability and dilution effects as the flood peaks. On an interannual scale, SPM variations are relatively low with slight temporal shifts observed in the formation and expansion of the turbid plume and peak SPM levels. The total SPM mass in the lagoon ranges from 0.2 to 0.3 × 104 tonnes during low-flow periods to 20-30 × 104 tonnes at the onset of flooding. We also discuss uncertainties associated with SPM determination, estimated at approximately 5–15%. This study leverages a unique database in West Africa and provides valuable insights into the hydro-sedimentary dynamics of Nokoué Lagoon.

Perspectives on total phosphorus response in rivers: Examining the influence of rainfall extremes and post-dry rainfall

Eutrophication is a significant environmental problem caused by nutrient loads from both point and non-point sources. Weather variables, particularly precipitation, affect the concentration of nutrients in water bodies, particularly those from non-point sources, in two contrasting ways. Heavy precipitation causes surface runoff which transports pollutants to rivers and increases nutrient concentration. Conversely, increased river flow can dilute the concentration, lowering it. This study investigates the impact of extreme precipitation, prolonged precipitation, and precipitation after a dry period on the total phosphorus concentration in the Moehne and Erft rivers in Germany, given the projected increase in frequency of extreme precipitation events and long drought periods due to climate change. The study comprises two parts: selecting extreme weather days from 2001 to 2021 and comparing observed Total Phosphorus concentrations with estimated concentrations derived from Generalized Additive Models and linear regression based on the discharge-concentration relationship. Changes in river TP concentration in response to continuous precipitation and precipitation after a dry period were also studied. Our results showed that during wet extreme and post-dry period rainfall events, TP concentration consistently surpassed expected values, underscoring the profound influence of intense rainfall on nutrient mobilization. However, we observed the impact of continuous rainfall to be non-unidirectional. Our work is distinguished by three key innovations: 1) addressing limitations in studying the effects of extreme weather on water quality due to limited temporal resolution, 2) incorporating both linear and non-linear modeling approaches for discharge-concentration relationships, and 3) performing a comprehensive analysis of temporal and spatial patterns of Total Phosphorus concentrations in response to varying rainfall patterns.

Investigation of compound occurrence of storm surge and river flood in Mikawa Bay, Japan, using typhoon track ensemble experiments

The risk of high river flow and peak storm surge superimposing in the estuary of small-and medium-sized rivers can be more severe during typhoon landfalls than at other times. In this study, 30 cases of typhoon track ensemble experiments for five rivers in Mikawa Bay, Japan, were evaluated using an atmospheric-river-ocean model. The results showed that storm surges coincided with high river flows when typhoons crossed the western side of Mikawa Bay, with the highest potential observed when typhoons passed northwest of the Bay. The average time discrepancy for the five rivers between the storm surge occurrence and increased river flow in the minimum time difference case was 48 min at the river mouth. Distinct trends in the time difference between a storm surge and river flow were observed for each river mouth. The order of time differences corresponded to the drainage area scale: Toyo (188 min), Umeda (112 min), Otowa (114 min), Sana (96 min), and Yagyu (88 min). Time difference trends also varied based on the distance between the typhoon center and each river mouth. For Toyo River, storm surges and high river flows did not substantially overlap, regardless of distance. However, for medium-and small-sized rivers, the time difference increased proportionally with the distance from the typhoon. The Yagyu River showed the highest potential for compound occurrence of a storm surge and river flood because of the synchronization of storm surge peaks and high river flow peaks, with a time difference of 1–2 h for small-and medium-sized rivers within 100 km2 of the basin.

Effect of water movement in frozen soil on long-term hydrological simulation of Soil and Water Assessment Tool in cold climate watershed in Hokkaido, Japan

ABSTRACT Despite the unique hydrological properties exhibited by frozen soil, its characteristics are often oversimplified in most distributed hydrological models, resulting in major errors in material cycle predictions in cold climate regions. This study aims to modify the Soil and Water Assessment Tool (SWAT), a semi-distributed hydrological model that originally assumes no water movement in frozen soil layers, by incorporating the dynamic change of soil permeability based on the degree of soil freezing, and to understand the effect of water movement in frozen soil on watershed hydrology. SWAT with frozen soil permeability (SWAT-FSP) was developed by adding two modules to the original SWAT: a heat conduction equation that considers the phase change of ice and liquid water and a frozen-soil percolation model that considers dynamic decrease in soil permeability due to soil freezing. The original SWAT and SWAT-FSP were set up in the Tokoro River watershed in northern Japan. The river flow and soil water dynamics during the snowmelt period (March–May) simulated using the original SWAT and SWAT-FSP were compared. The modified model significantly alters the soil water dynamics simulation to generate earlier soil water drainage and reduces the soil water content during the snowmelt period in years featuring weak soil freezing. Consequently, the SWAT-FSP estimated an earlier increase in river flow at the beginning of the snowmelt period and a smaller river flow in the middle of the snowmelt period as compared with the original SWAT. The modified model improved the overall performance in river flow simulation for the snowmelt period (March–May) of 2012–2019. The Nash-Sutcliffe efficiency obtained during the calibration period by the original SWAT was 0.602, and during the validation period it was 0.367. For the SWAT-FSP, it was 0.659 during calibration, and 0.639 during validation. Meanwhile, the SWAT-FSP showed unsatisfactory performance in 2014 and 2015, with underestimated snow water equivalent, indicating that improvements in the snowmelt/accumulation module may further enhance its accuracy. Our results showed that the dynamic change of soil permeability governed by the degree of soil freezing is an important factor affecting the water cycle of cold climate watersheds with seasonally frozen soil.

Climate change influences on the streamflow and sediment supply to the Chao Phraya River basin, Thailand

This study investigates the effects of climate change on the sediment loads of the Ping and Wang River basins and their contribution to the sediment dynamics of the lower Chao Phraya River basin in Thailand. The various climate models under different Representative Concentration Pathways (RCPs) scenarios are employed to project sediment loads in future. The findings indicate a significant increase in river flow approximately 20% in the Ping River (PR) and 35% in the Wang River (WR) by the mid-21st century and continuing into the distant future. Consequently, this is expected to result in sediment loads up to 0.33 × 106 t/y in the PR and 0.28 × 106 t/y in the WR. This escalation is particularly notable under the RCP 8.5 scenario, which assumes higher greenhouse gas emissions. Additionally, the research provides insights into the potential positive implications for the Chao Phraya Delta's coastal management. Without further damming in the Ping and Wang River basins, the anticipated rise in sediment supply could aid in mitigating the adverse effects of land subsidence and sea-level rise, which have historically caused extensive shoreline retreat in the delta region, particularly around Bangkok Metropolis. The paper concludes that proactive adaptation strategies are required to manage the expected changes in the hydrological and sediment regimes to protect vulnerable coastal zones and ensure the sustainable management of the Chao Phraya River Basin in the face of climate change.

Predicted variable river response at high and low flows due to groundwater abstraction changes in Chalk catchments

Improving low flows in Chalk streams by relocating groundwater abstraction further downstream is an idea that has become popular in the UK in recent years. Simulations using the Environment Agency's Hertfordshire Chalk Groundwater Model predict that reducing groundwater abstraction close to ephemeral or intermittent Chalk streams is more likely to increase river flows during high-flow conditions than during low flows. This finding helps to explain the apparent lack of observed benefit to river flows during drought periods in catchments where abstractions have been reduced. If abstraction reductions are predicted to result in more of an increase to high river flows than to low flows, they may risk contributing to increased flood likelihood downstream, without providing significant habitat protection during low flows. Conversely, it has also been found that, under certain circumstances, preferential benefits can be predicted for low flows. Simulations show that such benefits are most likely to manifest by relocating abstraction to downstream locations where groundwater levels are already below the base of the riverbed (e.g. due to existing abstraction or artificial channel modifications). Here, the varying degree of hydraulic connection between groundwater and river can result in preferential benefits to downstream low flows and reduced downstream flood risk. Thematic collection: This article is part of the Karst: Characterization, Hazards &amp; Hydrogeology collection available at: https://www.lyellcollection.org/topic/collections/karst

A methodology for integrating time-lagged rainfall and river flow data into machine learning models to improve prediction of quality parameters of raw water supplying a treatment plant

Abstract Rainfall and increased river flow can deteriorate raw water (RW) quality parameters such as turbidity and UV absorbance at 254 nm. This study aims to develop a methodology for integrating both time-lagged watershed rainfall and river flow data into machine learning models of the quality of RW supplying a drinking water treatment plant (DWTP). Spearman's rank non-parametric cross-correlation analyses were performed using both river flow and rain in the watershed and RW data from the water intake. Then, RW turbidity and RW UV254 were modelled, using a support vector regression (SVR) and an artificial neural network (ANN) under several prediction scenarios with time-lagged variables. River flow presented a very strong correlation with RW quality, whereas rainfall showed a moderate correlation. Time lags with maximum correlations between flow data and turbidity were a few hours, while for UV254, they were between 2 and 4 days, demonstrating varied time lags and a complex behaviour. The best performing scenario was the one that used time-lagged watershed rainfall and river flow as input data. The ANN performed better for both turbidity and UV254 than SVR. Results from this study suggest the possibility for new modelling strategies and more accurate chemical dosing for the removal of key contaminants.

The impact of rain‐on‐snow events on the snowmelt process: A field study

AbstractPrevious studies have primarily focused on the hydrological response of snowpack during rain‐on‐snow (ROS) events, with limited attention given to their subsequent stages, despite the significance of these stages. Therefore, this study selected two snow plots with similar initial parameters in the Qilian Mountains at an altitude of 4151 m. One of the snow plots underwent artificial rainfall simulation, and the changes in snow albedo, liquid water content, and snow depth of two snow plots were observed and analysed during the rainfall experiment and for a period of 7 days thereafter. The results indicate that ROS events significantly accelerate the rate of decrease in snow albedo and snow depth, increase the liquid water content within the snowpack, and these effects persist for several days after the rainfall event. Furthermore, the input of liquid water leads to rapid saturation of the snowpack, altering the transport mechanism of water within the snowpack, and transforming a process that would otherwise take a long time to complete into a short time. The decrease in snow albedo enhances the absorption of more energy by the snow, thereby accelerating snowmelt. Compared to natural snowmelt, ROS events cause the snowpack with high liquid water content to rapidly melt over a short period, resulting in a rapid increase in river flow, which may be one of the causes of ROS‐induced flooding. These research findings provide scientific insights for a better understanding of the disaster mechanisms associated with ROS events.

Main Physical Processes Affecting the Residence Times of a Micro-Tidal Estuary

Residence time is an important parameter linked to the water quality in an estuary. In this paper, we identify and analyze the main processes that affect the residence time of the Caloosahatchee River Estuary, a micro-tidal and mixed diurnal-semidiurnal estuary located in western Florida. Multiyear validated hydrodynamic hindcast results were coupled with an offline particle tracking model to compute the residence time of the estuary, which showed a strong seasonality driven by the river discharge. The residence time reduced with increasing river flow. The wind velocity and direction also affected the residence time. The influence of the wind was dependent on the magnitude of the river discharge. In general, upstream-directed wind increased residence time, while downstream-directed wind decreased residence time. Downstream wind during the dry period reduced residence time on average by a week. Processes such as water density gradient-induced circulation and particle buoyancy also influenced the residence time of the estuary. The outcomes of this study can be used to better understand the influence of the main physical processes affecting the residence time at other similar estuaries and to help in the management of the estuaries to improve their water quality.

Quantifying terminal white bands in Salix from the Yenisei river, Siberia and their relationship to late-season flooding

Key MessageWood fiber cell wall thickness best characterizes white bands found at the end of certain growth rings in Salix alba. Evidence suggests these features are related to late-season hydrology.Recent, record-breaking discharge in the Yenisei River, Siberia, is part of a larger trend of increasing river flow in the Arctic driven by Arctic Amplification. These changes in magnitude and timing of discharge can lead to increased risk of extreme flood events, with implications for infrastructure, ecosystems, and climate. To better understand the effect of these changes on riparian tree growth along the lower reaches of the Yenisei River, we collected white willow (Salix alba) cross sections from a fluvial fill flat terrace that occasionally floods when water levels are extremely high. These samples displayed bands of lighter colored wood at the end of certain annual growth rings that we hypothesized were related to flood events. To identify the characteristics and causes of these features, we use an approach known as quantitative wood anatomy (QWA) to measure variation in fiber cell dimensions across tree rings, particularly fiber lumen area (LA) and cell wall thickness (CWT). We investigate (1) which cell parameters and method to extract intra-annual data from annual tree rings best capture terminal white bands identified in Salix, and (2) if these patterns are related to flood magnitude and/or duration. We find that fiber CWT best captures terminal white bands found in Salix rings. Time series derived from CWT measurements correlate with July water-level durations, but at levels too low to be labeled flooding. Although both terminal white bands and July flooding have reduced since 1980, questions remain as to the cause of terminal white bands. Understanding how riparian vegetation responds to changes in hydrology can help us better manage riparian ecosystems and understand the impacts of a changing Arctic hydrological regime.

Residence, activity patterns and behaviour of the giant mottled eel Anguilla marmorata in two freshwater protected areas in the Philippines

Abstract Despite the giant mottled eel Anguilla marmorata being a widely distributed and locally exploited species throughout the Indo Pacific region, understanding of its life history, behaviour and movement ecology remains limited. Knowledge of animal spatial ecology is essential for the effective design and siting of aquatic protected areas. In the current study, acoustic telemetry was used to quantify residence and explore the activity patterns and behaviour of A. marmorata (n = 68) in two freshwater protected areas (FPAs) for the first time in the Cagayan River Basin, Philippines. The results demonstrated that FPAs of only 1 km length provided refuge for A. marmorata for an average of 25–26% of the tracked period. Residence and activity patterns varied with habitat type. In pool and riffle habitat, activity reduced with increased river flow, and eel, particularly larger individuals, were more strongly nocturnal than those in the deep pooled, slow flowing habitat. Typhoon events displaced many individuals, particularly in the pool and riffle habitat, with only 3% returning to the FPA within the study. Findings are discussed within the context of selecting FPA sites to optimize eel protection within catchments experiencing high non‐selective fisheries exploitation and other threats.

Managed Nitrogen Load Decrease Reduces Chlorophyll and Hypoxia in Warming Temperate Urban Estuary

Many urban estuaries worldwide suffer from excess phytoplankton and hypoxia (low oxygen) due to high nutrient loads. A common water quality management strategy is to require wastewater treatment facility upgrades. This case study examines Narragansett Bay, a warming temperate mid-latitude urban estuary with seasonal periodic hypoxia, during June through September from 2005 to 2019. Within this period, numerous facilities were upgraded to nitrogen removal over several years. The response of the bay is more consistent with “textbook” expectations for reduced chlorophyll and hypoxia than what was seen in many other systems—despite its complex coastline geometry, numerous river inputs, and widely-distributed treatment facilities. River flow drives inter-annual variability with increased load, density stratification, chlorophyll, and hypoxia in wet years. Mean 2013-2019 bay-wide total nitrogen load was 34% less than the 2005-2012 mean, a reduction of about 106 kg yr-1, comparable to the range of flow-driven inter-annual variations. Chlorophyll Index and Hypoxia Index event-based metrics applied to high-frequency time series observations at eight sites quantify exceedances of severe and moderate thresholds. Relatively steady 33% and 16% Chlorophyll Index declines, for severe and moderate thresholds, occurred from about 2007 to 2019. The Hypoxia Index declined markedly by 2009 and 2014 for severe and moderate thresholds, respectively, and remained at or near zero from 2014 to 2019. The load reduction explains chlorophyll and hypoxia declines better than physical processes including river flow, stratification, tidal variations, winds, sea level differences, and temperatures. River flow about 55% higher than the 2005-2019 mean would increase non-treatment facility loads by an amount comparable to the managed load decrease, so future wet summers could partially reverse the improvements. Long-term trends include warming of about 0.5°C decade-1, which reduces oxygen saturation by 0.1 mg l-1 decade-1. This rate is likely a lower bound for temperature-driven oxygen decreases, because warming can also accelerate phytoplankton growth and bacterial consumption. Without warming, the managed load decrease would have curtailed hypoxia more effectively. Climate trends should be at least as important to future eutrophication as the managed load decline because, in addition to warming influences, long-term increases in river flow would increase load and stratification.

Increased river flow enhances the resilience of spatially patterned mudflats to erosion

Estuarine mudflats are profoundly affected by increased coastal erosion and reduced sediment delivery from major rivers. Although managers are having difficulties to control the cause of increased coastal erosion, they can help to manage the resilience of mudflat ecosystems to erosion through river flow regulation. In this study, we associated the resilience of a mudflat ecosystem to erosion with various magnitudes of river flow using a mechanism-based eco-morphodynamic model. Ecosystem resilience was reported in terms of i) what range of erosion rate the system can withstand before function collapse (persistence), ii) at which point function can be recovered (recovery), and iii) the uncertainty of system response to disturbances (response uncertainty). Specifically, the function of intertidal mudflat was characterized by landscape heterogeneity, primary productivity, and sediment stabilization. In a case study of the Yellow River Estuary (YRE) of China, it is found that increased erosion induced a collapse of the functioning state. Once collapsed, the erosion rate at which mudflat could recovered was lower than the erosion rate at which mudflat collapsed. Increased river flow enhanced the resilience of the mudflat ecosystem to erosion by increasing sediment deposition rate, which was an important attribute in the interaction process driving ecosystem resilience. Furthermore, given the same river flow allocation, the system with dynamic grazer population was more resilient than the system with a constant grazer number, highlighting the importance of controlling mudflat aquaculture to optimize the performance of river flow regulation. Our modeling results are dependent on the environment with several assumptions, however, as a preliminary, we believe our work represents a fundamental shift to modeling ecosystem resilience based on the mechanism of bio-physical interactions rather than relying on just quantifying the vital rates of particular species to compare river flow scenarios.

Trends in Streamflow in Relation to Water Retention Structures: A Case Study in Bharathpuzha River Basin, India

Lack of availability of land, water and other natural resources along with climate change has caused a major threat for increasing the agricultural production on par with the increasing population. Bharathapuzha river is considered as the cradle of civilization in Kerala state, India. The river flow is highly affected by increased water use and reduced recharge caused due to increasing population, urbanization and unscientific management practices. Even though, watershed development activities in river basins help in conserving water in the upstream areas for agricultural, domestic and other uses, very few research have been done to understand its effect on the flow regime in the lower reaches. A number of dams, check dams and other conservation structures have been constructed in Bharathapuzha catchment area during the past and hence its effect on the downstream flow need to be studied. The calibrated and validated SWAT model was applied to Bharathapuzha river basin for studying the impact of watershed interventions on the water balance of the area. The simulated monthly streamflow was analyzed during 2007 to 2011 after addition of Water Retention Structures (WRS) @ 0.05%, 0.1% and 0.2% of the land area. The results indicated that even though the total annual flow decreased, the flow during the summer months (baseflow) increased due to the addition of the conservation structures. The increase in river flow was highest during the period January to April when the river had lean flow. It was found that SWAT model can be used as an effective tool to study the impact of water retention structures in a watershed. The conservation structures help to store water in the upper reaches for irrigation and domestic purpose, and at the same time it helps in increasing the summer flow. This helps to maintain a better environmental flow regime. Hence while planning the conservation measures in a watershed so as to meet the demand of the upstream users, care should be taken to avoid the negative impact that can happen in the downstream.

Taxation and public spending in Peru 2000-2018

&#x0D; In general, when the river flow increases, a scour phenomenon will occur, in which the substructure of the bridge, be it abutment and / or piers, will be affected, resulting in a partial or total collapse of the structure. All of the above is the key to achieving our research objectives, which is to carry out an evaluation and protection design against the hydraulic scour process of the Unocolla bridge in the city of Juliaca, Puno. The population will be the Unocolla bridge and the sample will be a substructure of the bridge. The method used is applied and its design is pure experimental, using quantitative methods, in which the research problem is described as realistic results. To determine the scour effects, topographic, hydrological and sedimentological information was collected to later carry out hydraulic modeling in the Hec-Ras program. Scour depths were determined in reference to pillars, determining in pillar 1 scour depth 1.2 m, in pillar 2 scour depth 2.46 m, in pillar 3 scour depth 1.2 m, in pillar 4 scour depth 1.2 m, for which the castling process is proposed as an alternative solution.

The Impact of Climate Change on Hydrological Regime of the Transboundary River Shu Basin (Kazakhstan–Kyrgyzstan): Forecast for 2050

The impact of regional climate change on the runoff and the regime of glacier- and snow-fed rivers in the transboundary river Shu basin between Kazakhstan and Kyrgyzstan is investigated. This study covered three of the most representative rivers of the Shu basin. It was based on the weather and gauging stations’ observation data in the river Shu basin — the northern Tien Shan. Based on the trend analysis, an increase in the average annual temperature and river discharge was identified within the observation period as a whole, and for the separate compared periods. Furthermore, the mean annual flow projections were made based on the methodology of the retrospective analysis of runoff and the rate of river flow increase for the observation period, and further extrapolation of data for the forecast period. According to the analysis, the mean annual flow for the considered rivers will be decreased by 25 to 30% on average by 2050. These findings are necessary for elaborating adaptation measures in water allocation for freshwater supply, irrigation and hydropower within this transboundary river.

Effects of climate and land use changes on stream flow of Chitral river basin of northern highland Hindu-Kush region of Pakistan

Adverse impacts of climate change on the ecosystem have been a significant concern in the last decades. However, the studies related to the impacts of climate change on water resources, especially in northern Pakistan are of great importance as this region is the main supplier of freshwater to the downstream areas. So, the present study was carried out in Chitral River Basin (CRB) to investigate the long term climatic and topographic changes. Spatiotemporal datasets from MODIS Land Cover Type product (MCD12Q1) from 2001 to 2018, ground-based observational climatic and hydrological data were used. Moreover, the Mann-Kendall trend test, linear regression analysis, correlation, and Sen’s slope values for the mean annual and seasonal flows were assessed. The acquired results show that land use changes are the key non-natural factors in transforming the ecological and hydrological processes of CRB. The mixed and evergreen forest, shrubland, savannas, and barren land respectively decreased from 0.07 to 0.03%, 0.07 to 0.05%, 3.64 to 3.25%, and 70.10 to 67.17%, from 2001 to 2018. In addition, a considerable increment in snow cover from 8.79% to 10.71%, and slight increment in grasslands, wetlands, and croplands were also found between the period of observation. In addition, total annual precipitation and mean annual stream flow showed slight upward trends. Annual increment in total rainfall and snow covered area could be the possible reasons for the observed increased river flow.