Search Results (12)

This study investigates the complex interaction of biophysical and meteorological factors that drive evapotranspiration (ET) in saline environments. Leveraging a total of 182 cloud-free Landsat 5/8 time-series data from 1988 to 2019, we employed the Surface Energy Balance System (SEBS) model to quantify ET and investigate its relationships with soil salinity, vegetation cover, groundwater depth, and landscape metrics. We validated the predicted ET at two experimental sites using ET observation calculated by a water balance model. The result shows an R² of 0.78 and RMSE of 0.91 mm for the SEBS predicted ET, indicating high accuracy of the ET estimation. We detected abandoned saline farmland patches across Hetao and extracted the normalized difference vegetation index (NDVI), salinization index (SI), and the predicted ET for analysis. The results indicate that ET is negatively correlated with SI with a Pearson correlation coefficient (r) up to −0.7, while ET is positively correlated with NDVI (r = 0.4). In addition, we designed a control-variable experiment in the Yichang subdistrict to investigate the effects of groundwater depth, land aggregation index, soil salinity index, and the area of abandoned saline farmland patches on ET. The results indicate that increased NDVI could significantly enhance ET, while smaller saline farmland patches exhibited greater sensitivity to groundwater recharge, with higher averaged ET than larger patches. Moreover, we analyzed factor importance using Lasso regression and Random Forest (RF) regression. The result shows that the ranking of the importance of the features is consistent for both methods and for all the features, with NDVI being the most important (with an RF importance score of 0.4), followed by groundwater table depth (GWTD), and the influence of the surface area of abandoned saline farmland being the weakest. We found that smaller patches of abandoned saline farmland were more sensitive to changes in groundwater levels induced by nearby irrigation, affecting their averaged ET more dynamically than larger patches. Decreasing patch size over time indicates ongoing changes in land management and ecological conditions. This study, through a multifactor analysis of ET in abandoned saline farmland and its intrinsic factors, provides a reference for evaluating the dry drainage efficiency of abandoned saline farmland in a dry drainage system. Full article

Climate change (CC) is expected to cause significant changes in weather patterns, leading to extreme phenomena. Specifically, the intensity of precipitation extremes is continuously escalating, even in regions with decreasing average precipitation levels. Given that CC leads to long-term shifts in weather patterns and may affect the precipitation characteristics (i.e., frequency, duration, and intensity) directly related to groundwater table fluctuations and soil erosion phenomena, it has the potential to significantly affect soil slope instabilities. In turn, slope stability and the structural integrity of nearby structures and infrastructure will be affected. Accordingly, the present paper focuses on the impact of CC on the geohazard of soil slope instability by considering both hydrological aspects, i.e., the impact on rainfall intensity on the groundwater table and the geotechnical aspects of this complex problem. The findings reveal that the impact of CC on potential slope instabilities can be detrimental or even beneficial, depending on the specific site and water conditions. Therefore, it is essential to do the following: (a) collect all the available data of the area of interest, (b) assess their variations over time, and (c) examine each potentially unstable slope on a case-by-case basis to properly mitigate this geohazard. Full article

Areas excluded from agricultural production are susceptible to the presence of beaver families. The most significant changes occur during the initial period, when agricultural utilization is abandoned and beavers establish their presence on the land. During this period, some parcels remain uncultivated, while agricultural activities persist in neighboring areas. This situation is accompanied by the destruction of beaver dams, especially during periods of abundant water resources, and notably during intensive fieldwork. The article presents field studies aimed at determining the extent to which constructed and operational beaver dams contribute to changes in groundwater levels in drained peatland areas. In order to protect and sustainably use peat soils, it is necessary to maintain their high moisture content by ensuring a high groundwater level elevation. This can be achieved through the use of existing damming structures in the area (levees, weirs). Beaver dams can also serve a similar function, blocking the outflow of water from peat lands by raising the water level and consequently retaining it naturally. The specific objective was to develop principles for verifying factors influencing the effects of beaver dam construction on groundwater levels in fields within their range of influence. The water table levels within the study area during rainless periods were influenced by water levels in ditches, dependent on beaver activity in the nearby river. Beaver activities, manifested through dam construction, were influenced by periodic water resources in the river, defined by the cumulative monthly precipitation. Factors affecting groundwater levels in rainless periods on the plots also included the distance from the river cross-section and the permeability of soils expressed by the filtration coefficient of the active layer. Beaver dams had the greatest impact on stabilizing the water table in the soil profile closest to the river. Full article

Among the techniques for capturing nearby groundwater, the covered horizontal well (draining gallery) stands out in its different types of water mine, qanat, and cimbre. The water collected by these means is used to supply people and livestock, in irrigation, in the movement of hydraulic devices, etc. Because they are carried to the surface by gravity (without the need for energy) and because only the recharging of the groundwater table that takes place after the rains are captured, they serve as models for sustainable water use. The measured flow is variable depending on the rainfall and infiltration, but the quality of the water makes it its own water resources of great interest at the local level. The study area is the territory of the Southeast of Spain (more than 22,000 km²), with a rich hydraulic heritage. The research is a regional analysis (diachronic and compared) of several socio-hydric systems, with extensive fieldwork. Full article

There are currently at least five aircraft runways built on the reclaimed coral sand foundations in the South China Sea (SCS). The seismic dynamics and stability of the revetment breakwaters and nearby aircraft runways built on reclaimed lands with coral sand in the SCS deserve attention. Taking the reclamation engineering in the SCS as the background, this study performed several centrifuge shaking table tests (N = 50 g) to explore the seismic dynamics and stability of a revetment breakwater and a nearby aircraft runway built on a reclaimed coral sand foundation. It is revealed that the revetment breakwater, aircraft runway, and their coral sand foundation have intensively responded to the excitation of seismic waves. The pore water pressure accumulates in the coral sand foundation; however, the accumulation amplitude is not significant. As a result, only soil softening, rather than liquefaction, has occurred in the coral sand foundation. The final residual subsidence of the revetment breakwater and aircraft runways are both about 0.5 mm, indicating that they are finally in a stable state. Through comparative study, it is found that the pore water pressure in the loose coral sand foundation is much easier to accumulate, and the corresponding acceleration amplification effect is also more significant. It means that a loose coral sand foundation is more detrimental to the seismic stability of the revetment breakwaters and airport runways. Full article

Coupling surface and groundwater for a better understanding of the hydrologic response in arid basins is essential for managing water resources. The study aims to integrate surface water (SW) and groundwater (GW) modeling in an arid environment and to identify groundwater sources at Hadat Ash-Sham farm station in the Al-Lusub watershed, located in the western part of Saudi Arabia. The curve number (CN) method for SW modeling is primarily used to estimate GW potential recharge based on a developed correlation equation between event-based rainfall and potential recharge, which is processed in the Hydrologic Engineering Center-Hydrologic Modeling System (HEC-HMS) software. Monthly potential recharge is utilized to compute GW modeling in MODFLOW. Van Mullem’s equation is used to calculate hydraulic conductivity (K) from CN. The calibration of steady-state GW modeling reveals that the K (from Van Mullem’s equation) is within the range of measured K in the field. The transient groundwater modeling phase concludes that the groundwater system in the Al-Lusub watershed can be interpreted based on two different scenarios. The first is that an extra recharge from a nearby watershed flows through the geological structure into a downstream area. The second scenario involves potential recharge from surface water flowing on the Al-Lusub watershed’s mainstream bed. Validation reveals a strong relationship between predicted and observed water tables. The root mean square error (RMSE) for Scenarios 1 and 2 are 0.6 m and 0.7 m, respectively. Further investigation is needed to determine the region’s most common scenario. Full article

The underwater acoustic channel is remarkably dependent on the considered scenario and the environmental conditions. In fact, channel impairments differ significantly in shallow water with respect to deep water, and the presence of external factors such as snapping shrimps, bubbles, rain, or ships passing nearby, changes of temperature, and wind strength can change drastically the link quality in different seasons and even during the same day. Legacy mathematical models that consider these factors exist, but are either not very accurate, like the Urick model, or very computationally demanding, like the Bellhop ray tracer. Deterministic models based on lookup tables (LUTs) of sea trial measurements are widely used by the research community to simulate the acoustic channel in order to verify the functionalities of a network in certain water conditions before the actual deployment. These LUTs can characterize the link quality by observing, for instance, the average packet error rate or even a time varying packet error rate computed within a certain time window. While this procedure characterizes well the acoustic channel, the obtained simulation results are limited to a single channel realization, making it hard to fully evaluate the acoustic network in different conditions. In this paper, we discuss the development of a statistical channel model based on the analysis of real field experiment data, and compare its performance with the other channel models available in the DESERT Underwater network simulator. Full article

Data for the years 2001–2020 on changes in the amount of rainwater in the Roztocze National Park (RNP) in the catchment area of the Świerszcz River (Poland) were investigated to evaluate the possibility of using rainwater in the park for various purposes in the context of ongoing climate variability. An analysis of data from the RNP’s Integrated Monitoring of the Natural Environment showed that the average annual air temperature increased by 2.1 °C over the 20-year period, while the amount of precipitation decreased, especially in the winter seasons. These changes periodically led to a negative hydrological balance. As an effect, the groundwater table was gradually lowering, the flow of the Świerszcz River was reduced, and there were periodic shortages of water feeding the Echo Ponds. Water shortages also negatively affected the flora and fauna of the RNP. In order to quantitatively protect the Park’s water resources, a proposition was made to build a rainwater management system at the Animal Breeding Centre in Florianka to provide water for watering Polish Konik horses, flushing toilets, washing cars and agricultural equipment, and fire-prevention purposes. The excess water would be discharged to a nearby pond, which is an amphibian breeding site. It was estimated that the system was capable of meeting 100% of the demand for lower-quality water in the summer period. Moreover, it was determined that 9109 m³ of rainwater could be obtained annually from the roofs of all public utility buildings located in the RNP. Full article

Saving water is a major challenge to increase environmental sustainability, particularly in semi-arid regions where most table grapes are produced. Water use is driven by atmospheric demand, which combines effects of solar radiation (prominent factor), wind, air temperature and humidity. Covering table grapes with transparent plastics is spread in many regions. Covers lower incoming solar radiation and wind speed, changing air temperature and humidity. This study assessed the effects of two plastic covers on reference evapotranspiration (ET₀) in comparison to the open field. For two years, two vineyards (cv. Victoria) trained to overhead trellis systems (tendone) were covered with two transparent polyethylene sheets: an agrotextile fabric (C), and a commercial film (S). The sheet spectrophotometric properties were analyzed and the radiometric coefficients calculated. Micrometeorological data were recorded in the covered vineyards and in a nearby uncovered one. ET₀ was calculated for June and July using the simplified Penman–Monteith equation. The coefficient of transmissivity to total photosynthetic radiation, a proxy of net radiation, was 73% for cover C and 83% for cover S. On average, ET₀ decreased by 35% under cover C and 31% under cover S. Hence, in addition to providing protection from external agents, covers represent a valid tool for saving water in table grape viticulture; nevertheless, their radiometric properties should be considered and optimized to better achieve this goal. Full article

This paper reviews the site investigation field data and access work performed between 2016 and 2019 in the study area located close to Gun-dong mine. The research was aimed at defining the cause of sinkholes and their relationship with the underlying karstic limestone bedrock and nearby mining activities. Only a limited number of small sinkholes appeared in 2014, 2016, and 2018 in the agricultural land close to the limestone mine. The previously open pit mine started its underground operations in 2007. Since then, the mine has developed, and is now comprised of, large underground excavations at several levels below the surface. The studies carried out concluded that the appearance of sinkholes may be related to a general lowering of the groundwater table because of nearby agricultural and mining activities and also due to over-extraction of water due to increased urban use. Whilst these are the best determinations, this paper identifies missing elements of the previous investigations mentioned above, some issues with the interpretation of poorly prepared borehole logs and the improper preservation of borehole cores. The authors make recommendations for a systematic approach for implementation of an investigation strategy. This paper concludes that the appearance of sinkholes is a natural phenomenon, developing over geological time. However, human intervention contributes to sinkhole formation, which in urban areas may result in human, property, and economic losses. A better understanding, based on a methodical approach and suitable technologies, can determine the causes of sinkholes and can lead to the formulation of solutions and the implementation of economically and socially acceptable mitigation measures. Full article

A detailed hydrogeological study was carried out due to the recent occurrence of unexpected problems associated with the flooding of the water table during excavations in the area of a major urbanization work in Madrid. The numerous exploratory drilling excavations carried out allowed for the development of a conceptual model of the complex hydrogeological functioning in clay formations in an urban area. The clays have very little natural recharge, and the underground flow is highly conditioned by the topography and a fold-fault. Modelling with MODDFLOW confirmed and quantified this conceptual model and also allowed for the design of an efficient network of 1.5 km-long drainage trenches. The design of this drainage network was influenced by the difficult balance that must be respected in order not to contaminate the water with sulphates from the nearby gypsum substrate. This is to guarantee the quantitative and qualitative sustainability of the groundwater. The follow-up and monitoring of the water tables and the quality of the groundwater for more than a year after the excavation of the drainage trenches guaranteed the results of the research. Full article

Channel incision isolates flood plains, disrupts sediment transport, and degrades riparian ecology. Reactivation and periodicity of incision may affect the water table and hydrological conditions far beyond the stream margin. Long-term incision and its recent acceleration along Iron Springs Creek, North Dakota, USA, has affected adjacent ecosystems. An agricultural surface drain empties directly into the original spring-fed source of the creek, which triggered channel erosion both up- and downstream. Historical maps, recent LiDAR, and field surveying were used to characterize incision since ditch excavation in 1911. Although the soils are sandy, small hydrological gradients impede natural drainage in the surrounding stabilized dunes. Incision resulting from expanded drainage and increased precipitation has been as much as 5 m. Numerical models of lateral groundwater profiles corroborated with field measurements show that the nearby water table responds quickly, becoming deeper and less variable. With 1 m of recent incision, model evapotranspiration rates are decreased 50% to 15% from the channel margin to 1 km, respectively, and the hydropattern disrupted >1 km. Species diversity is reduced and floristic quality is 25% less near the drain. A near-channel solution to erosion—fencing out cattle—failed to mitigate the problem because a broader watershed approach was necessary. Full article