Search Results (1,256)

The Law enforcement profession is known to impart high stress. Members of Special Weapons and Tactics (SWAT) teams are allocated particularly demanding law enforcement operations and may therefore attain high fitness levels but may accumulate excessive stress. Heart rate variability (HRV), an assessment of time differences between heartbeats, likely indicates holistic load in field settings. To date, though, little research measuring HRV has been conducted involving SWAT units. The purpose of this study was to explore HRV measurements following (1) annual firearms qualification and (2) potential stress exposure with respect to completion time on an anaerobically taxing obstacle course. Officers with greater obstacle course performance were hypothesized to also exhibit greater HRV. HRV was also expected to stratify personnel more effectively than heart rate. Prospective 3-lead ECGs were obtained from a cohort of male SWAT operators (n = 15) with 5.2 ± 4.3 years of experience at three time points throughout one training day. HRV was assessed by time, frequency, and non-linear domains. Differences between baseline and post-training values were significant as assessed by the Wilcoxon signed-ranks test for heart rate, SDRR, LF, HF, and SD2. An enter-method linear regression model predicted post-training HF HRV by obstacle course time; r² = 0.617, F (1,6) = 9.652, p = 0.021. Anaerobic performance may be highly valuable in SWAT units. HRV analysis may also be beneficial in measuring the psychophysiological impact of SWAT activities. Full article

The freshwater discharge from catchments along the Gulf of Alaska, termed Alaska discharge, is characterized by significant quantity and variability. Owing to subarctic climate and mountainous topography, the Alaska discharge variations may deliver possible impacts beyond the local hydrology. While short-term and local discharge estimation has been frequently realized, a longer time span and a discussion on cascading impacts remain unexplored in this area. In this study, the Alaska discharge during 1982–2022 is estimated using the Soil and Water Assessment Tool (SWAT). The adequate balance between the model complexity and the functional efficiency of SWAT suits the objective well, and discharge simulation is successfully conducted after customization in melting calculations and careful calibrations. During 1982−2022, the Alaska discharge is estimated to be 14,396 ± 819 m³⋅s⁻¹⋅yr⁻¹, with meltwater contributing approximately 53%. Regarding variation in the Alaska discharge, the interannual change is found to be negatively correlated with sea surface salinity anomalies in the Alaska Stream, while the decadal change positively correlates with the North Pacific Gyre Oscillation, with reasonable time lags in both cases. These new findings provide insights into the relationship between local hydrology and regional climate in this area. More importantly, we provide rare evidence that variation in freshwater discharge may affect properties beyond the local hydrology. Full article

In this study, we analyzed the predictions of hydrological droughts in the Lam Chiang Kri Watershed (LCKW) by using the Soil and Water Assessment Tool (SWAT) and streamflow data for 2010–2021. The objective was to assess the streamflow drought index (SDI) for 5-, 10-, 25-, and 50-year return periods (RPs) in 2029 and 2039 in two representative concentration pathway (RCP) scenarios: the moderate climate change scenario (RCP 4.5) and the high-emission scenario (RCP 8.5). The SWAT model showed high accuracy (R² = 0.82, NSE = 0.78). In RCP4.5, streamflow is projected to increase by 34.74% for 2029 and 18.74% for 2039, while in RCP8.5, a 37.06% decrease is expected for 2029 and 55.84% for 2039. A historical analysis indicated that there were frequent short-term droughts according to SDI-3 (3-month-period index), particularly from 2014 to 2015 and 2020 to 2021, and severe droughts according to SDI-6 (6-month-period index) in 2015 and 2020. The RCP8.5 projections indicate worsening drought conditions, with critical periods from April to June. A wavelet analysis showed that there is a significant risk of severe hydrological drought in the LCKW. Drought characteristic analysis indicated that high-intensity events occur with low frequency in the 50-year RP. Conversely, high-frequency droughts with lower intensity are observed in RPs of less than 50 years. The results of this study highlight an increase in severe drought risk in high emission scenarios, emphasizing the need for water management. Full article

Investigations into the impacts of climate change on water conservation capacity in the upper Mekong River Basin (UMRB) are important for the region’s sustainability. However, quantitative studies on isolating the individual contribution of climate change to water conservation capacity are lacking. In this study, various data-driven SWAT models were developed to quantitatively analyze the unique impact of climate change on water conservation capacity in the UMRB. The results reveal the following: (1) From 1981 to 2020, the annual water conservation capacity ranged from 191.6 to 392.9 mm, showing significant seasonal differences with the values in the rainy season (218.6–420.3 mm) significantly higher than that in the dry season (−57.0–53.2 mm). (2) The contribution of climate change to water conservation capacity is generally negative, with the highest contribution (−65.2%) in the dry season, followed by the annual (−8.7%) and the rainy season (−8.1%). (3) Precipitation, followed by evaporation and surface runoff, emerged as the critical factor affecting water conservation capacity changes in the UMRB. This study can provide insights for water resources management and climate change adaptations in the UMRB and other similar regions in the world. Full article

Extreme flood events present a significant challenge for operators and managers of large drinking water reservoirs. Detailed flood response analysis can predict the hydrology response of a reservoir to changing climate conditions and can aid in managing the reservoir in anticipation of extreme events. Herein, the Soil and Water Assessment Tool (SWAT), a watershed model, was used in conjunction with a reservoir management model, the Operational Analysis and Simulation of Integrated Systems (OASIS) model, to evaluate extreme flood events across a set of initial reservoir storage capacities across various CMIP6 climate scenarios. The SWAT model was calibrated and validated with PRISM climate data in conjunction with land and soil cover data and multi-site gauged stream discharges. The validated model demonstrated satisfactory performance (NSE = 0.55 and R² = 0.56) for total reservoir inflow. The resulting inflow values from SWAT were utilized to set up a calibrated/validated OASIS model (NSE = 0.55 and R² = 0.68). OASIS was then used to assess alternative operating rules for the reservoir under varying climate scenarios (RCP4.5 and RCP8.5) and extreme events (synthetic hurricanes). Focusing on a major reservoir in the Northeastern United States, the analysis of the reservoir response was based on (1) reservoir volume–elevation curve, (2) daily reservoir inflow, (3) daily precipitation, (4) spillway flow, and (5) reservoir evaporation. Projected future scenarios indicate a >20% increase in precipitation in April compared to historical records, coupled with likely reduced runoff from November to March. With extreme conditions most likely in the month of April, RCP4.5 and RCP8.5 projections suggest that most scenarios result in a 10–15% increase in the mean of 3D30Y runoff volumes, and a 150% increase under the most extreme conditions. For 7D30Y runoff volumes in April, the RCP4.5 and RCP8.5 analyses reveal an increased likelihood of the reservoir elevation reaching overspill flow levels during the latter half of the simulation period (2020 to 2080). Our findings indicate that simulations with SWAT coupled with OASIS can assist reservoir managers in regulating water levels in anticipation of extreme precipitation events. Full article

Water ecological problems involve flood, drought, water pollution, destruction of water habitat and the tense relationship between humans and water. Water ecological problems are the main problems in the development of countries all over the world. In terms of ecological protection, China has put forward the ecological red line policy. Water ecology is an important component of the ecosystem, and the delineation of the water ecological red line is an important basis for ecological protection. Based on ecosystem services, this paper tries to determine the red line of the water ecology space and tries to solve various water problems comprehensively. Based on the ecosystem services accounting method, the SWAT (soil and water assessment tool) model was used to simulate the spatial–temporal dynamic quantities of water purification and rainwater infiltration services in the upper reaches of the Hanjiang River. The basin was divided into 106 sub-basins and 1790 HRUs (hydrological response units). Water quality data taken from 8 sites were used to verify the simulation results, and the verification results have high reliability. The grid scale spatialization of water quality and rainwater infiltration is realized based on HRU. The seasonal characteristics of hydrological regulation and control services were analyzed, the red line of hydrological regulation and control in the upper reaches of the Hanjiang River was defined, and the dynamic characteristics of water ecological red line were analyzed. According to the research results, the water ecological protection strategy of the basin is proposed. The prevention and control of water pollution should be emphasized in spring and summer, the prevention and control of rain flood infiltration in autumn and winter, and the normal monitoring and management should be adopted in the regulation and storage. The results of this study can provide scientific reference for water resources management and conservation policy making. Full article

Based on the principle of water supply and demand flow and the natural flow of water, this paper analyzes the flow direction and discharge of water resources in the study area. In order to provide scientific and systematic implementation suggestions for regional water resource protection management and ecological compensation, a SWAT (Soil and Water Assessment Tool) model was constructed to quantify the water resource supply of the upper Hanjiang River basin at three spatial scales: pixel, sub-basin, and administrative unit. The water demand at the three spatial scales was calculated using the LUCC (Land Use and Land Coverage) and water consumption index. The supply and benefit zones under different spatial and temporal scales were obtained. Simultaneously, this study uncovered the spatiotemporal dynamics inherent in water resource supply and demand, alongside elucidating the spatial extent and flow attributes of water supply. The ecological compensation scheme of water resource supply–demand was preliminarily determined. The findings indicate an initial increase followed by a decrease in both the water supply and demand in the upper reaches of the Han River, accompanied by spatial disparities in the water supply distribution. The direction of the water supply generally flows from branch to main stream. The final ecological compensation scheme should be combined with natural conditions and economic development to determine a reasonable financial compensation system. Full article

Urbanization in the Haihe River Basin in northern China, particularly the upstream mountainous basin of Baiyangdian, has significantly altered land use and runoff processes. The runoff is a key water source for downstream areas like Baiyangdian and the Xiong’an New Area, making it essential to understand these changes’ implications for water security. However, the exact implications of these processes remain unclear. To address this gap, a simulation framework combining SWAT+ and CLUE-S was used to analyze runoff responses under different land use scenarios: natural development (ND), farmland protection (FP), and ecological protection (EP). The model simulation results were good, with NSE above 0.7 for SWAT+. The Kappa coefficient for CLUE-S model validation was 0.83. The further study found that from 2005 to 2015, urban construction land increased by 11.50 km² per year, leading to a 0.5–1.3 mm rise in annual runoff. Although urban expansion continued, the other scenarios, which emphasized farmland and forest preservation, slowed this growth. Monthly runoff changes were most significant during the rainy season, with annual runoff in ND, FP, and EP varying by 8.9%, 10.9%, and 7.7%, respectively. While the differences in annual runoff between scenarios were not dramatic, these findings provide a theoretical foundation for future water resource planning and management in the upstream mountainous area of Baiyangdian and offer valuable insights for the sustainable development of Xiong’an New Area. Additionally, these results contribute to the broader field of hydrology by highlighting the importance of considering multiple land use scenarios in runoff change analysis. Full article

Change in land use and land cover (LULC) is crucial to freshwater ecosystems as it affects surface runoff, groundwater storage, and sediment and nutrient transport within watershed areas. Ecosystem components such as wetlands, which can contribute to the reduction of water pollution and the enhancement of groundwater recharge, are altered by LULC modifications. This study evaluates how wetlands in the Big Sunflower River Watershed (BSRW) have changed in recent years and quantified their impacts on streamflow, water quality, and groundwater storage using the Soil and Water Assessment Tool (SWAT). The model was well calibrated and validated prior to its application. Our study showed that the maximum increase in wetland areas within the sub-watersheds of interest was 26% from 2008 to 2020. The maximum changes in reduction due to the increase in wetland areas were determined by 2% for streamflow, 37% for total suspended solids, 13% for total phosphorus (TP), 4% for total nitrogen (TN), and the maximum increase in shallow groundwater storage by 90 mm from 2008 to 2020 only in the selected sub-basins. However, the central part of the watershed experienced average declines of groundwater levels up to 176 mm per year due to water withdrawal for irrigation or other uses. This study also found that restoration of 460 to 550 ha of wetlands could increase the reduction of discharge by 20%, sediment by 25%, TN by 18%, and TP by 12%. This study highlights the importance of wetland conservation for water quality improvement and management of groundwater resources. Full article

Many dammed reservoirs in dry climate conditions witness high sediment inflow rates due to higher soil erodibility, yet there are limited actual sediment influx measurements. Therefore, this study first applies the Soil and Water Assessment Tool (SWAT) hydrologic model to simulate reservoir sedimentation inflow to the Haditha Reservoir. Next, utilizing sediment inflows estimated by the SWAT model, the Trap Efficiency Function (TEF) is employed to estimate its remaining storage capacity and its useful life at multiple reservoir water levels. Calibration (1986–1997) and validation (1998–2007) of the SWAT model were conducted at three streamflow gaging stations and one sediment station located upstream of the reservoir. Results show that the SWAT model performed better during calibration than during the validation period for all streamflow and sediment gaging stations. In addition, modeled streamflow and sediment predictions were relatively more accurate on a monthly scale than on a daily scale. Simulated daily sediment inflow to the reservoir demonstrates slightly lower accuracy than daily streamflow, where the Coefficient of Determination (R²) and Nash-Sutcliffe Efficiency values are 0.34 and 0.32 in the case of sediment load, compared to 0.39 and 0.33 for streamflow, respectively. Reservoir storage capacity for the period (1986–2005) shows a continuous decrease with time at all reservoir water levels, which indicates an increase in sediment accumulation. According to measurements taken between 1986 and 2005, sediment accumulation has reduced the reservoir’s capacity by approximately 15% at a water level of 112 m (the lowest water level in the reservoir). During the same period, the storage capacity loss at 147 m (the design working water level in the reservoir) was calculated to be 35%. Over 19 years of operation (1986–2005) at the 147-m water level, the total sediment buildup in the reservoir is estimated at 3.2 million tons. Notably, about one-third of this sediment was deposited in the five-year span from 2000 to 2005. Full article

Water conservation is a crucial indicator that measures the available water resources needed for maintaining regional ecological services and socioeconomic development. The Yiluo River Basin plays an essential role in water conservation in the Yellow River Basin, which is one of the most important river basins with vulnerable ecological conditions and a large population in China. However, previous studies have a limited understanding of the distribution of water conservation in the Yiluo River Basin. To address this knowledge gap, we developed a SWAT model to evaluate water conservation in the Yiluo River Basin with high spatial and temporal details on a monthly scale. From a monthly perspective, water conservation accumulation primarily took place in July (54.6 mm), August (23.5 mm), and September (33.2 mm), which are in the flood season. From 1966 to 2018, we found a significant 47% reduction in basin-wide water conservation, and the reduction was primarily influenced by meteorological conditions and underlying surface dynamics. The results of the temporal correlation analysis identified precipitation as the most significant factor influencing water conservation, while the spatial correlation analysis revealed that potential evapotranspiration, vegetation, and elevation had the highest spatial correlation with water conservation. By combining SWAT outputs on the HRU (hydrological response unit) scale with the spatial distribution of HRUs, the study achieved the visualization of the spatial distribution of water conservation, identifying Luonan County, Luanchuan County, and Luoning County as the key regions that experienced water conservation decline over the past decades. These findings advance our understanding of the distributions of water conservation and their key driving factors in the study area and provide valuable policy implications to support ecological protection and water resource management in the Yellow River Basin. Full article

Surface runoff is a key component of the hydrological cycle and is essential for water resource management and water ecological balance in river basins. It is important to accurately reveal the spatial and temporal dynamics of regional surface runoff over long time scales and to quantify the impacts of climate change and human activities on surface runoff changes for sustainable water resources management and utilization. In this study, the Minjiang River Basin (Chengdu section) was selected, which has significant natural and anthropogenic variations, and a comprehensive analysis of runoff and its drivers will help to formulate an effective regional water resource management strategy. We mainly used SWAT to simulate the monthly-scale runoff in the Chengdu section of the Minjiang River Basin from 1990 to 2019 and combined SWAT-CUP to perform sensitivity analysis on the model parameters and Partial Least Squares Structural Equation Modeling (PLS-SEM) to quantitatively analyze the main drivers of the changes in surface runoff. The results show that the average multi-year runoff in the Minjiang River Basin (Chengdu section) ranges from 628.96 to 1088.46 mm, with an average value of 834.13 mm, and that the overall annual runoff in the past 30 years shows a fluctuating tendency. The goodness-of-fit of the PLS-SEM model is 0.507; the validity and reliability assessment indicated that the model was reasonable, and its results showed that economic and landscape factors had significant negative impacts on runoff changes, while natural factors had positive impacts on runoff changes, with path coefficients of −0.210, −0.131, and 0.367, respectively. Meanwhile, this study also identified two potential indirect impact pathways, i.e., the economic factors had an indirect negative impact on runoff by changing the distribution of landscapes, and the natural factors had indirect negative impacts on runoff by influencing economic activities, reflecting the complex interactions among economic activities, landscape distribution, and natural factors in influencing surface runoff. This study provides a research framework and methodology for quantitatively modeling surface runoff and the analysis of influencing factors in watersheds, contributing to a deeper scientific understanding of long-term runoff changes and the contribution of their drivers. Full article

Jiamusi is situated in Heilongjiang Province, China, in the center of the Sanjiang Plain. The 1980s’ overplanting of paddy fields resulted in a decrease in groundwater levels, scarcity of groundwater resources, and frequent earth collapses. Examining and safeguarding the groundwater resources in this region has emerged as a crucial subject. In light of this, this paper uses the remote sensing water balance method and the SWAT distributed hydrological model to calculate groundwater resources in the Jiamusi area. It also conducts scientific experiments by examining various factors, including rainfall, the degree of water supply, soil type, and land use. The measured monthly runoff of Jiamusi City’s Tongjiang and Fuyuan City’s hydrology stations was utilized to establish the model parameters for the SWAT model. A preliminary assessment of the distribution features of shallow groundwater in the Jiamusi area is conducted using the two methodologies mentioned above, and the following results are reached: (1) Tongjiang Hydrological Station and Fuyuan Hydrological Station both had good runoff modeling results, with R² and NS values of 0.81, 0.77, and 0.77, 0.75, respectively. (2) The SWAT model works well for assessing groundwater resources. Between 2010 and 2016 (two preheating years), Jiamusi’s average groundwater recharge was 61.03 × 10⁸ m³, with a recoverable amount of 27.4 × 10⁸ m³. (3) Based on the remote sensing water balancing approach, the average exploitable quantity of groundwater recharge in the Jiamusi area between 2008 and 2016 is 23.94 × 10⁸ m³, while the average recharge in the area is 53.2 × 10⁸ m³. (4) The Jiamusi metropolitan area is the core of the groundwater phreatic reservoir water reserves, which progressively decline in both the northeast and southeast directions. It falls to the southwest as Fuyuan City’s center. The Songhua River’s main stream area near Tongjiang City has the least volume of water reserves in the phreatic layer, and the area’s groundwater reserves converge to the southeast and northwest, where surface water makes up the majority of the water resources. Full article

To keep groundwater levels stable, Jinan’s government has implemented several water management measures. However, considerable volumes of dissolved organic carbon (DOC) can enter groundwater via water exchange, impacting groundwater stability. In this study, a SWAT-MODFLOW-RT3D model designed specifically for the Yufu River Basin is developed, and part of the code of the RT3D module is modified to simulate changes in DOC concentrations in groundwater under different artificial recharge scenarios. The ultimate objective is to offer valuable insights into the effective management of water resources in the designated study region. The modified SWAT-MODFLOW-RT3D model simulates the variations of DOC concentration in groundwater under three artificial recharge scenarios, which are (a) recharged by Yellow River water; (b) recharged by Yangtze River water; and (c) recharged by Yangtze River and Yellow River water. The study shows that the main source of groundwater DOC in the basin is exogenous water. The distribution of DOC concentration in groundwater in the basin shows obvious spatial variations due to the influence of infiltration of surface water. The area near the upstream riverbank is the earliest to be affected. With the prolongation of the artificial recharge period, the DOC concentration in groundwater gradually rises from upstream to downstream, and from both sides of the riverbank to the surrounding area. By 2030, the maximum level of DOC in the basin will exceed 6.20 mg/l. The Yellow River water recharge scenario provides more groundwater recharge and less DOC input than the other two scenarios. The findings of this study indicate that particularly when recharge water supplies are enhanced with organic carbon, DOC concentrations in groundwater may alter dramatically during artificial recharge. This coupled modeling analysis is critical for assessing the impact of recharge water on groundwater quality to guide subsequent recharge programs. Full article