查看更多>>摘要：The estimation of actual evapotranspiration is a difficult issue in hydrological research, particularly in the scarcely observed region. Deep learning (DL) has been increasingly used in the field of hydrology in recent years. In this study, we investigated the ability of DL on actual evapotranspiration estimation using three sets of controlled experiments at a typical region with scarce observations, the Qinghai-Tibetan Plateau. The results suggest that the DL model can utilize a few key types of observation data to simulate actual evapotranspiration, and more in-situ observation data types did not significantly improve the accuracy of DL simulations. A multisource DL model established by integrating data from distantly distributed stations showed a better performance than the model built separately using data at individual sites. Moreover, further analysis of climate pattern and input data correlation was conducted for the similarity of stations for multi-source learning of the DL model. Using inputs in the lead-time period can improve the simulation of daily ET by DL. Compared with traditional process-based physical methods, the DL model is more flexible to simulate actual evapotranspiration in areas with insufficient observed data such as the Qinghai-Tibetan Plateau. The results of this study highlight the potential power of DL model to improve the actual evapotranspiration estimation in the scarcely observed region.
查看更多>>摘要：Land-ocean coordinated management is an important wisdom for environmental protection and pollution prevention of marine and river systems. Taking Liao River and Estuarine as an example, the pollution characteristics, temporal and spatial distribution and change features of Polycyclic Aromatic Hydrocarbons (PAHs) in sediments in recent 20 years were studied from two different analysis perspectives of land and ocean. The research showed that the pollution of PAHs in the sediments of Liao River and Estuarine was not optimistic. The concentration of sigma(16)PAHs was 48-28,000 ng/g. The carcinogenic risk to humans shouldn't be ignored, which could cause the loss of life expectancy 0.03-4.2 years. The traceability analysis showed that the use and combustion of fossil fuels were the main sources of PAHs. In addition, the leakage of oil during the intensive transportation of ships in coastal waters might also contribute to PAHs. The concentrations of PAHs had obvious temporal and spatial distribution characteristics. Spatially, estuaries < tributaries < main streams; temporally, wet season < normal season < dry season in Liao River. Whereas, the variation of PAHs in estuarine sediments was slight. In the past 20 years, the concentration of PAHs in Liao River had increased first and then decreased, reaching maximum in 2010; However, the concentration of PAHs seldom decreased in estuarine sediments, in which showed a more serious situation of PAHs pollution control.
Poozan, AbolfazlWestern, Andrew WilliamBurns, Matthew JamesArora, Meenakshi...
11页
查看更多>>摘要：A major problem associated with sealing native soils with impervious surfaces in urban areas is reduced groundwater recharge. This in turn reduces stream baseflows which has serious implications for freshwater ecosystems. To address this problem, the use of stormwater infiltration systems is becoming increasingly common worldwide. There is, however, substantial uncertainty on the fate of infiltrated stormwater and its interactions with downslope vegetation. This study aimed to investigate the role of vegetation on the amount of infiltrated stormwater reaching the stream. A model using MIKE SHE was constructed, calibrated, and validated based on a real infiltration system which features extensive vegetation between the site of stormwater infiltration and the stream. We then used the calibrated model to predict the amount of infiltrated stormwater reaching the stream in the absence of vegetation. We also predicted the impact of infiltrated stormwater on the evapotranspiration downslope of the system. The results showed that the performance of the model was satisfactory, and the model captured the overall groundwater dynamic very well. The amount of infiltrated stormwater reaching the stream increased by about 17 percent in the absence of vegetation. The model also predicted that evapotranspiration would be 13 percent lower in the warmer months if stormwater was not infiltrated upslope. The results suggest that the choice of location of infiltration systems should consider the potential of vegetation to intercept infiltrated water and impact on achievement of the design objectives, which, in this case, included restoring baseflow. Where increasing the baseflows is not a priority, the increased evapotranspiration afforded by stormwater infiltration could provide important microclimate benefits.
查看更多>>摘要：Drought is a complex and slow-moving disaster that is difficult to monitor and define. This study, therefore, aims to demonstrate the characteristics of recent droughts occurring from 2008 to 2015 over South Korea using a process-based land and hydrologic model, Weather Research and Forecasting-Hydro modeling system (WRFHydro). To drive the standalone WRF-Hydro, gridded meteorological data (5 km) were generated using stationbased observations and the Parameter-elevation Regressions on Independent Slopes Model (PRISM). The model was calibrated and evaluated using inflow observations at four locations with dams; for 2008-2010 (calibration) and 2011-2015 (evaluation), it demonstrated average R2 values of 0.80 and 0.75, respectively. While Standardized Precipitation Index is used for calculating meteorological drought using precipitation from PRISM, Standardized Soil Moisture Index and Standardized Streamflow Index, at different timescales, are used to calculate agricultural and hydrological droughts, respectively, with WRF-Hydro simulations. The correlation coefficients between SPI and both SSFI and SSMI were calculated to detect their response times. The hydrological and agricultural droughts showed response times 0.5-1 month later than meteorological drought. In 2008-2015, agricultural and hydrological drought events occurred 1.6 times per year on average in South Korea, whereas meteorological droughts occurred 4.3 times per year on average. Agricultural and hydrological droughts lagged behind meteorological droughts by up to 53, 65, and 83 days, when using 1-, 3-, and 6-month SPI, respectively. Moreover, hydrological droughts were less severe than meteorological droughts due to the propagation of drought by attenuation. This study demonstrates that WRF-Hydro can be used to quantitatively determine the different types of drought events and their propagation, which could help policy makers manage drought risks.
查看更多>>摘要：In this study, we have compared heat and solute transport in a discrete fracture using numerical modeling. Fracture aperture heterogeneity was described using geostatistical properties with fracture aperture means of up to 1000 mu m, variances of 10,000 mu m(2) and isotropic correlation lengths up to 10 m. Groundwater flow in the matrix was assumed to be negligible and flow in the fracture was set to values typical for natural groundwater conditions with velocities less than 100 m/day and associated hydraulic gradients of less than 0.05. A uniform isotropic thermal conductivity of 2 W/m ? was set for the matrix. Based on 50 realizations, three-dimensional and two-dimensional conduction in the matrix and in the fracture, respectively, play an important role in controlling the development and the shape of the thermal plume under natural flow conditions. In contrast, solute transport exhibits limited penetration depth in the matrix. The results of this research indicate that, contrary to solute transport in discrete fracture settings where channeling is sometimes a major contributor to solute migration rates, no significant thermal channeling is observed under natural groundwater flow conditions. The use of tracer experiments or the monitoring of solute transport in fractured rock will not therefore provide a reliable prediction of the migration of heat in the same setting.
查看更多>>摘要：Identifying the effect of climate variability and human activities on runoff changes is scientifically essential for understanding hydrological processes and sustainable water resources management. This study selected 64 catchments located in the mainland of China to quantify the effects of different driving forces on runoff changes. Results showed that annual runoff in the Haihe river basin, Liaohe river basin, and Yellow river basin exhibited significantly decreasing trends from 1965 to 2018 (P < 0.05), whereas the Northwest river basin had positive trends in the annual runoff. Meanwhile, the Pettitt test method was applied to detect abrupt changes in annual runoff. Compared to the rivers in Southern China, the northern rivers had significant abrupt changes in annual runoff and mostly occurred in the 1990 s. The Choudhury-Yang equation based on the Budyko hypothesis was used to assess the sensitivity of runoff to precipitation (P), potential evapotranspiration (ET0), and the land surface (n) changes. The results showed that runoff was more sensitive to P and n, compared to ET0. Attribution analysis revealed that P was the dominant factor in the Northwest river basin, Southwest river basin, Yangtze river basin, Southeast river basin, and Pearl river basin, whereas the changes in n were responsible for runoff changes in the Liaohe river basin, Haihe river basin, Yellow river Basin, Songhuajiang river basin, and Huaihe river basin. The land surface changes (n) were resulted from vegetation restoration, urbanization expansion, construction of reservoirs/check dams, and surface water withdrawals, leading to significant changes in river runoff in recent years. The findings can provide good insight for water resources management across China.
NSTL
Elsevier