Surface Water Distribution Research Articles

Occurrence, distribution, and potential health risks of psychoactive substances in Chinese surface waters

Ten psychoactive substances (PSs) and metabolites were identified and quantified in 217 surface water samples collected across China to reveal the occurrence, distribution, and potential health risks in Chinese surface waters. The results showed the ubiquitous occurrence of caffeine (CFI), paraxanthine (PXT) and cotinine (CTN) at all the monitored sites, the concentrations of which ranged from not detected to 3460 ng L−1, while the remaining PSs were detected at trace levels (<50 ng L−1). High concentrations of diet-related PSs (CTN, CFI, and PXT) typically occurred in areas with high population densities. Traditional drugs tended to occur in megacities and the illegal manufacturing bases of the illicit drugs. Emerging drugs were found to be very popular across the whole country, with no significant differences among the samples. The risk assessment results suggest that drinking water containing these PS residues posed no potential human health risk in any life stage. However, the age-dependent risk quotients (RQs) of the 5 assessed PSs for the 12 age intervals ranged from < 1.0 × 10−7 to 0.005. In terms of the evaluated life stages, the RQs for early stages (from birth to <2 years) were significantly higher than the RQs for other stages.

Investigation on trace metal speciation and distribution in the Scheldt estuary

The biogeochemical behavior of Cd, Co, Cr, Cu, Ni and Pb along the historically polluted Scheldt estuary (Belgium - The Netherlands) was investigated in this study. As never studied before in this area, labile trace metals were measured using the passive sampling technique of Diffusive Gradients in Thin-films (DGT), while total dissolved and particulate trace metal concentrations were assessed using classic active sampling techniques. This dual approach allowed us to highlight the variations of trace metal speciation and distribution in the estuarine surface waters, considering environmental and physicochemical gradients along the transect. The large data set obtained was then compared with literature data of historical measurements along the Scheldt (from 1980 until now), but also from other estuaries. As emphasized by our results, trace metal mobility and partitioning along the Scheldt estuary was mainly driven by biogeochemical reactions which were strongly influenced by gradients of specific estuarine physico-chemical parameters, such as salinity, turbidity, temperature and so on. Hence, all species of trace metals displayed a non-conservative behavior. More precisely, dissolved labile fractions of trace metals showed higher levels in the middle estuary, where many solubilization and remobilization processes occurred due to turbulent mixing mechanisms and an increasing salinity. Our study confirmed the decreasing trend historically observed for particulate metals along the Scheldt, as well as the rising concentrations recorded for dissolved trace metals which might also lead to an increase of their labile fraction measured by the DGT. Finally, these preliminary results suggested that a more regular monitoring of labile metal along the Scheldt estuary is essential to have an in-depth understanding of trace metal speciation and to review bioavailability of trace metals within estuarine ecosystems.

African Humid Period Precipitation Sustained by Robust Vegetation, Soil, and Lake Feedbacks

AbstractThe African Humid Period (∼11,000–5,000 years before present) was the most recent of several precessionally paced wet intervals during which an increase in the Northern Hemisphere summer incoming solar radiation intensifies the West African Monsoon leading to dramatic changes over northern Africa. However, insolation anomaly alone is not sufficient and feedbacks are essential for further amplification of the monsoon. The most significant feedbacks derive from the land surface, arising from changes to vegetation, soil properties, and distribution of surface water. We show that in contrast to previous studies that have explored the individual impacts of these feedbacks, a modern climate model yields a much greater increase in precipitation in response to their collective effect. Agreement with proxies is improved while the desert‐steppe transition is pushed further northward than in any previous study. In the West African Sahel, intensities of summer daily mean and extreme precipitation increase by 150% and 90%, respectively.

GNSS characterization of hydrological loading in South and Southeast Asia

SUMMARY The elastic response of the lithosphere to surface mass redistributions produces geodetically measurable deformation of the Earth. This deformation is especially pronounced in South and Southeast Asia, where the annual monsoon produces large-amplitude hydrological loads. The Myanmar–India–Bangladesh–Bhutan (MIBB) network of about 20 continuously operating Global Navigation Satellite Systems (GNSS) stations, established in 2011, provides an opportunity to study the Earth's response to these loads. In this study, we use GRACE temporal gravity products as an estimate of long-wavelength surface water distribution and use this estimate in an elastic loading calculation. We compare the predicted vertical deformation from GRACE with that observed with GNSS. We find that elastic loading inferred from the GRACE gravity model is able to explain the phase and much of the peak-to-peak amplitude (typically 2–3 cm) of the vertical GNSS oscillations, especially in northeast India and central Myanmar. GRACE-based corrections reduce the RMS scatter of the GNSS data by 30–45% in these regions. However, this approach does not capture all of the seasonal deformation in central Bangladesh and southern Myanmar. We show by a synthetic test that local hydrological effects may explain discrepancies between the GNSS and GRACE signals in these places. Two independent hydrological loading models of water stored in soil, vegetation, snow, lakes and streams display phase lags compared to the GRACE and GNSS observations, perhaps indicating that groundwater contributes to the observed loading in addition to near-surface hydrology. The results of our calculations have implications for survey-mode GNSS measurements, which make up the majority of geodetic measurements in this region. By using the GNSS data together with estimates of hydrological loading from independent observations and models, we may be able to more accurately determine crustal motions caused by tectonic processes in South and Southeast Asia, while also improving our ability to monitor the annual monsoon and resulting water storage changes in the region.

Spatial distribution of polycyclic aromatic hydrocarbons in the water–sediment system near chemical industry parks in the Yangtze River Delta, China

The Yangtze River Delta (YRD) is one of the most populated and economically prosperous regions in China and contains numerous chemical industry parks. To understand the distribution and sources of polycyclic aromatic hydrocarbons (PAHs), surface water and sediment samples were collected from areas around the industrial parks. The total concentrations of 19 PAHs in water and sediment were 32.98–286 ng L−1 and 15.14–5355 ng g−1, respectively. The highest PAH concentrations in water and sediment were found in samples from Wuxi city, which were dominated by high molecular weight (HMW) PAHs, and strongly influenced by fine chemical parks. HMW compounds dominated in the sediment with PAHs containing four and five rings accounting for 61% of the sedimentary ΣPAHs, PAHs in water were dominated by low molecular weight (LMW) compounds (PAHs with two and three rings represented >68% of ΣPAHs). The results of isomeric ratio analysis and principal component analysis with multiple linear regression indicated that the PAH concentrations in water and sediment near the YRD chemical parks are strongly influenced by industrial emissions. The fugacity fraction approach was applied to explain the trend for water–sediment exchange of 16 priority PAHs, which showed that net fluxes for most were from the sediment into water. The results indicated that the LMW PAHs were in a non-steady state in the sediment–water system. An ecological risk assessment showed that most sites were low to medium risk, but one site was high risk.

Computational investigation on surface water distribution and permeability of porous asphalt pavement

ABSTRACT This paper used the finite element method to analyse surface water distribution characteristics on porous asphalt layer under unsaturated seepage, and further compared the critical rainfall intensity of porous asphalt pavements with different design parameters. In this study, the Richards equation was used to describe the unsaturated seepage, and the results were validated with experimental data. The results show that when the water accumulates on the pavement surface, it would firstly emerge at the lowest level of pavement along the longitudinal direction, and then spread along transverse and longitudinal directions. The water depth has no remarkable difference along the longitudinal direction while it differs a lot among different transverse positions. The distribution of surface water depth was analysed and the correlation between the surface water coverage in the transverse direction and the rainfall intensity was established with high R-square values. For pavements with different geometries, the porous layer thickness has the most remarkable effect on the critical rainfall intensity of porous asphalt pavements.

Precipitation and aridity constraints from paleolakes on early Mars

AbstractThe ancient climate of Mars remains an enigma despite the abundance of in situ and remote-sensing data revealing hydrological activity in the past. The crux of this debate—informed by geomorphic studies, chemical alteration observations, and numerical climate models—is the amount, distribution, and nature of surface water and precipitation (i.e., rain vs. snow). Here, we combined measurements of 96 open- and closed-basin lakes with simple hydrological balances to constrain catchment-averaged precipitation, PT, integrated over a given runoff episode of indeterminate length during early Mars history. We included 13 systems containing both open- and closed-basin lakes, providing fully bounded precipitation estimates (coupled systems). We show that, on average, PT was ≳4 m and ≲159 m; however, local precipitation was spatially variable and consistent with a complex, planetwide climate. Aridity indexes of open-basin lakes indicate some regions may have been at least as humid as semiarid terrestrial environments. Our results offer widely distributed, quantitative hydro-climate constraints that can be used to test paleoclimate model scenarios, working toward bridging the gap between geological observations and climate theory for early Mars.

Comparison of Surface and Subsurface Water Distribution Uniformity Under Center Pivot Irrigation System for Sugarcane in Colombia

The objective of this work was to determine the variability in the uniformity of the applied sheet of irrigation, on the surface of the soil, with central pivoting equipment in sugarcane, with the uniformity of humidity that occurs in the soil profile. With ASABE standard S.436.1, as the test procedure, moisture measurements were taken with a TDR equipment in three soil depths of 0–0.2 m, 0.2–0.4 m, and 0.4–0.6 m every 5 m away. Three evaluations were made, in the central pivot of the length of 430 m (58 ha), with two different application sheets, 12 mm and 22 mm, in two different years (2018 and 2019), that is, in two sugarcane production cycles. The crop age of 2–3 months is the same in the two cycles. Comparisons of the sheets on the soil surface are made with those of moisture collected before irrigation (AR), 24 h after irrigation (24hDR), and 48 h after an irrigation (48hDR). The coefficient of uniformity of Christiansen for the sheet on the 75, 78, and 80% was in values of 81.4 and 82.2%, and for the soil moisture at different depths, the applied sheet and the initial soil moisture condition were decisive. The uniformity in the soil profile was never higher than 5% of the presence on the surface, and on occasions, the sheet results became lower. Results showed that under the conditions of the crop and the operation of the equipment, the determination of the uniformity in the surface is a parameter that can be used to define the performance of an irrigation system.

Predicting hot spots of aquatic plant biomass in a large floodplain river catchment in the Australian wet-dry tropics

Conservation planning processes and wetland management require spatial estimations of aquatic habitats to support the maintenance of aquatic biodiversity. However, physical access to several wetlands and freshwater habitats can be restricted due to difficult topography and technological limitations associated with ground-based observations. In addition to these constraints, the distribution of some aquatic primary producers in freshwater habitats and floodplains that are difficult to reach further complicates large-scale assessment of aquatic habitats using traditional field-based techniques. The main objective of this study is to predict the spatial distribution of hot spots of primary producers (aquatic plant biomass) and assess large-scale inundation patterns in a large floodplain wetland (Flinders catchment) in the wet-dry tropics of Australia. To this end, remote sensing biophysical indicators (vegetation and inundation) were integrated with flood water depth in a classification tree model. Results indicate that in terms of floodplain total inundation, the Flinders wetland hydrology is rather restricted immediately after the summer wet season, the period when most primary production happens. While this can be attributed to the fact that much of the observed annual variability (93%) in rainfall and surface runoff (95%) occur during the wet season, post flood recession patterns are indicators that underpin the somewhat limited alimentation of the Flinders floodplain during this period. As observed in this study, post flood inundation extents in the summers of 2009 and 2019 declined by approximately 89% and 87% within fourteen and ten days, respectively. Despite having a significantly higher magnitude than the 2009 summer flood event, the 2019 extreme ‘big wet’ period did not translate to higher floodplain productivity (aquatic plant biomass and surface water distribution) immediately after summer as was the case in 2009. Furthermore, the predicted extents of aquatic plant biomass and total floodplain inundation in the downstream Flinders show substantial temporal variation and suggest the floodplain wetland hydrology is largely driven by inter-annual changes in annual rainfall. The extents of these hot spots of biomass accumulation were found to be considerably associated with total floodplain inundation extent (r=0.94), rainfall (r=0.81), and discharge (r=0.68). Furthermore, advance statistical analyses show that downstream discharge and rainfall over the Flinders are significantly correlated (r=0.72). In addition to this, observed amplitudes of discharge and rainfall in extreme wet and dry years coincided with floodplain inundation patterns and distribution of hot spots of primary producers. While these relationships emphasize the importance of flow in the nourishment of the downstream catchment, they further corroborate the composite influence of local rainfall and discharge on total floodplain inundation and hot spots of primary producers.

Analysis of scattering characteristics from inland bodies of water observed by CYGNSS

Measurements made by spaceborne Global Navigation Satellite System Reflectometry (GNSS-R) instruments have shown strong reflected power over inland waters that has been attributed to coherent scattering coming from the first Fresnel zone. Previous work in the field has shown the ability of GNSS-R to observe the global surface water distribution by generating dynamic maps of wetlands and other inundated areas. These maps can be generated by leveraging the large difference in received power of the GNSS signals as they reflect from water surfaces compared to land. In this paper, we utilize a full-forward scattering model approach to evaluate the accuracy of these maps. The CYGNSS End-to-End Simulator (E2ES) was extended to include the contributions from coherent surface scattering in heterogeneous regions where the area around the specular point contains both water and land in complex geometries. The simulator is then used to analyze the accuracy of a current approach to estimate the surface water content in the first Fresnel zone from a single measurement, called a fractional water in footprint approach. We find that contributions to the total received power by the scattering from outside the first Fresnel zone as well as CYGNSS instrument effects impact the accuracy of this approach. Furthermore, the measured signal from calibration scattering targets is compared to the results of simulation to validate the scattering model. The work shows that the variability of the peak reflected power over inland bodies of water due to the scene heterogeneities should be accounted for in designing retrieval algorithms to map wetland extent.

Controls on species distribution and biogeochemical cycling in nitrate-contaminated groundwater and surface water, southeastern Australia

A detailed study of groundwater and surface water nitrate over four seasons across an area of varied landuse provided insights into the mechanisms that underlie accumulation and transport of nitrate. High nitrate concentrations found in a significant percentage of surface water and shallow groundwater samples are due to anthropogenic contamination. Statistics (PCA, ANOVA, parsimonious model and general linear regression) were used to explore the relationship between NO3− and land use, and confirmed that areas of high NO3− concentration are associated with dairy pasture and horticulture. Seasonally, NO3− levels are greater during winter, the wettest part of the year. Values of δ15N showed that most nitrate is sourced from livestock waste, with a smaller contribution from synthetic fertilizer. Direct wash-off of animal waste from dairy farms results in higher NO3− concentrations in surface water than in groundwater. Denitrification is an important NO3− attenuation mechanism which reduces NO3− to NH4, as demonstrated by the PCA analysis, which showed positive correlation of NO3− concentrations with dissolved oxygen and negative correlations with NH4+, Fe2+and Mn2+; the latter two species may act as the electron donors necessary for reduction of NO3−. The often high NO3− concentrations in shallow groundwater are decreased by denitrification, which can occur at relatively shallow depths (<3 m). The relatively small NO3− concentrations in deeper groundwater are due partly to denitrification, but more to originally lower NO3− concentrations, as the age of deeper groundwater shows that it was recharged before agriculture was established in the study area. Overall, the study demonstrates the usefulness of hydrogeochemical characterisation and multivariate statistics in the evaluation of impacts of agricultural land-use on regional N cycling. In particular, the results show that efforts to mitigate NO3− pollution from farms should concentrate more on wash-off of animal waste than the contribution of nitrogenous synthetic fertilizer.

Automatic Surface Water Mapping Using Polarimetric SAR Data for Long-Term Change Detection

Mapping the distribution and persistence of surface water in a timely fashion has broad value for tracking dynamic events like flooding, and for monitoring the effects of climate and human activities on natural resource values and biodiversity. Traditionally, surface water is mapped from optical imagery using semi-automatic approaches. However, this process is time-consuming and the accuracy of results can vary among image interpreters. In recent years, Synthetic Aperture Radar (SAR) images have been increasingly used. Microwave signals sensitive to water content make SAR systems useful for mapping surface water, saturated soils, and flooded vegetation. In this study, a fully automatic method based on robust stepwise thresholding was developed to map and track the change in the extent of surface water using Polarimetric SAR data. The application of this method in both Radarsat-2 and Sentinel-1 data in central Ontario, Canada demonstrates that the developed robust stepwise thresholding approach could facilitate rapid mapping of open water areas with a promising accuracy of over 95%. In addition, the time-series extent of surface water extracted from May 2008 to August 2016 reveals the dynamic nature of surface inundation, and the trend was consistent with the local precipitation data.

Nutrient Fluxes Associated With Submarine Groundwater Discharge From Karstic Coastal Aquifers (Côte Bleue, French Mediterranean Coastline)

Determination of submarine groundwater discharge (SGD) from karstic coastal aquifers is important to constrain hydrological and biogeochemical cycles. However, SGD quantification using commonly employed geochemical methods can be difficult to constrain under the presence of large riverine inputs, and is further complicated by the determination of the karstic groundwater endmember. Here, we investigated a coastal region where groundwater discharges from a karstic aquifer system using airborne thermal infrared mapping and geochemical sampling conducted along offshore transects. We report radium data (223Ra, 224Ra, 228Ra) that we used to derive fluxes (water, nutrients) associated with terrestrial groundwater discharge and/or seawater circulation through the nearshore permeable sediments and coastal aquifer. Field work was conducted at different periods of the year to study the temporal variability of the chemical fluxes. Offshore transects of 223Ra and 224Ra were used to derive horizontal eddy diffusivity coefficients that were subsequently combined with surface water nutrient gradients (NO2- + NO3-, DSi) to determine the net nutrient flux from SGD. The estimated DSi and (NO2- + NO3-) fluxes are 6.2 ± 5.0 *103 and 4.0 ± 2.0 *103 mol d-1 per kilometer of coastline, respectively. We attempted to further constrain these SGD fluxes by combining horizontal eddy diffusivity and 228Ra gradients. SGD endmember selection in this area (terrestrial groundwater discharge versus porewater) adds further uncertainty to the flux calculation and thus prevented us from calculating a reliable flux. Additionally, the relatively long half-life of 228Ra (5.75 y) makes it sensitive to specific circulation patterns in this coastal region, including sporadic intrusions of Rhone river waters that impact both the 228Ra and nutrient surface water distributions. We show that SGD nutrient fluxes locally reach up to 20 times the nutrient fluxes from a small river (Huveaune River). On a regional scale, DSi fluxes driven by SGD vary between 0.1 and 1.4 % of the DSi inputs of the Rhone River, while the (NO2- + NO3-) fluxes driven by SGD on this 22 km long coastline are between 0.1 – 0.3 % of the Rhone River inputs, the largest river that discharges into the Mediterranean Sea.

STUDY ON THE VARIATION OF SURFACE WATER BASED ON LANDSAT IMAGERY IN GUILIN

Abstract. Using remote sensing technology to study the distribution and change of surface water is an important application of remote sensing technology. It is also an important means of water resources protection. This paper takes the Lijiang River Basin in Guilin, Guangxi as the research object. Landsat satellite images were used as the data source. After classifying the images, the surface water distribution area of Lijiang River Basin in Guilin City was extracted, and the area change and its spatial distribution are compared. On this basis, combined with the actual situation in Guilin, the paper analyzes the causes of surface water distribution change in Lijiang river basin from two aspects of natural factors and human factors.

Human Activities and Climate Variability Affecting Inland Water Surface Area in a High Latitude River Basin

Spatiotemporal changes in the surface area of inland water bodies have important implications in regional water resources, flood control, and drought hazard prediction. Although inland water bodies have been investigated intensively, few studies have looked at the effect of human activities and climate variability on surface area of inland waters at a larger scale over time and space. In this study, we used MODIS (MOD13Q1) images to determine water surface area extent at 250 m spatial resolution. We then applied this algorithm with MOD13Q1 images taken at 16-day intervals from 2000 to 2018 to a large river basin in China’s northeast high latitude region with dense stream network and abundant wetlands to investigate spatiotemporal distribution and dynamics of inland water bodies. The study identified 209 ponds, lakes, and reservoirs with an average total surface area of 2080 km2 in the past 19 years. The total water surface area fluctuated largely from 942 km2 to 5169 km2, corresponding to rainfall intensity and flood. We found that the total water surface area in this high latitude river basin showed an increasing trend during the study period, while the annual precipitation amount in the river basin also had an increasing trend concurrently. Precipitation and irrigation significantly contributed to the monthly change of water surface area, which reached the highest during June and August. The increase of water surface area was significant in the lower basin floodplain region, where agricultural irrigation using groundwater for rice production has progressed. Four nationally important wetland preserves (Zhalong, Xianghai, Momoge, and Chagan Lake) in the river basin made up nearly 50% of the basin’s total water surface area, of which Zhalong, Xianghai, and Momoge are designated by The Ramsar Convention as wetland sites of international importance. Seasonally, these water bodies reached their maximal surface area in August, when both the monsoon weather and agricultural discharge prevailed. This study demonstrates that water surface area in a high latitude river basin is affected by both human activities and climate variation, implying that high latitude regions will likely experience more changes in surface water distribution as global climate change continues and agriculture becomes intensified.

Enhanced photodegradation of diphenhydramine in aqueous solution containing natural sand particles.

Understanding the effects of natural solid particles on the phototransformation of pharmaceuticals in aqueous environments is very important, but studies on this are still limited. In this study, natural sands were selected as a solid particle model due to their wide distribution in surface waters during the rainy season, and the phototransformation of diphenhydramine (DP) in the presence of the sands was investigated. The kinetic studies showed that the natural sands exhibited significant photocatalytic activity for the DP photodegradation, and the activity varied depending on their sources. Scavenging experiments and electron paramagnetic resonance analysis demonstrated that O2−˙ and ˙OH were produced in the irradiated natural sand systems, and O2−˙ played a more important role than ˙OH in the photodegradation of DP. The results obtained from H2O2 treatment and deoxygenation experiments verified that the generation of radicals was mainly attributed to the low content of natural organic matter (NOM) in the sands. The possible reaction mechanism was that the NOM in the sands was excited and became triplet-state NOM after irradiation, and then induced the generation of free radicals through an electron transfer mechanism, resulting in DP oxidation. This work indicated that natural sand particles were a key factor affecting the phototransformation of drugs, and should be considered in evaluating their fate in natural waters.

ВНУТРІШНЬОРІЧНА ДИНАМІКА ВМІСТУ ОРГАНІЧНИХ ТА БІОГЕННИХ РЕЧОВИН У ВОДІ ОЗЕРА ВЕРБНОГО (м. КИЇВ)

The results of investigations of the dissolved organic substances and nutrients distribution in surface and bottom water of the Verbne lake in 2018-2019 are presented and analysed. In particular the annual values of the total dissolved organic substances content by parameters of permanganate and bichromate oxidizabilities are difined. Also the seasonal dynamics of such different organic compounds as humic acids, fulvic acids, carbohydrates and protein-like substance in surface and bottom water are considered. The concentration alterations of the nitrogen, phosphorus and silicon combinations of nutrients from seasonal factor are studied. The major hydrochemical characters of water (pH, dissolved oxygen concentration, degree of oxygen saturation of water, chemical oxygen demand) and their correlation with the seasonal changes of the general dissolved organic substances content and nutrient compounds are adduced. The traditional seasonal distribution of these organic substances indicates a good self-cleaning ability of the Verbne lake. The received results testify that the investigated Verbne lake belong to a evtrophic reservoir in which hydrobionts actively develop and there are important processes of accumulation and destruction of these substances that essentially influences on their component composition. The ecological features of the chemical composition of this water object are largely determined both by natural processes and anthropogenic pressure, which is manifested not only in the direct entering into the water products of human activity, but also indirectly, as a result of changes in the physical, chemical and biological factors in the aqueous environment. Monitoring of annual and seasonal changes of the total and components content dissolved organic substances and nutrients in the water along with other hydrochemical and hydrobiological indices makes it possible to assess the ecological state of water objects.

The effect of the top soil layer on moisture and evaporation dynamics

AbstractUnderstanding the effect of the top soil layer on surface evaporation and water distribution is critical to modeling hydrological systems. However, the dependency of near‐surface soil moisture and fluxes on layering characteristics remains unclear. To address this uncertainty, we investigate how the arrangement of soil horizons affects the evaporation and soil moisture, specifically, the near‐surface soil moisture, through the combination of numerical simulations and evaporation experiments. The characteristics of fluxes and moisture from different soil profiles are then used to understand the soil layering conditions. Results show that the top soil layer can significantly affect the evolution of soil moisture profiles and evaporation dynamics, the extent of which depends on the layering sequence, thickness, and properties of each layer. The soil systems consisting of a thick coarse (C) layer overlying a fine (F) layer, or a very thin F layer overlying a C layer exhibit near‐surface moisture, temperature and fluxes nearly identical to that of a homogeneous C system; in these cases, a homogeneous C soil could be used to represent the above two layered systems. However, some soil profiles cannot be described by a single set of soil properties, nevertheless, they show distinct characteristics that can serve as indicators for soil layering conditions, e.g., “first slowly then rapidly” decreasing dynamics of near‐surface soil moisture. As some characteristics are not unique to layered soil, the combined information including the near‐surface soil moisture defined at different depths and evaporation behavior of an entire drying cycle can be used to better characterize the layering conditions.

Potential assessment of non-automatic and automatic modernization alternatives for the improvement of water distribution supplied by surface-water resources: A case study in Iran

Water shortages have led farmers within irrigation districts to resort to groundwater resources. In this scenario, a decrease in those water losses due to improper operational management within the districts may halt the increasing trend of groundwater overexploitation. This study aims to examine the impact of improving operational management in irrigation districts both to provide reliable surface water distribution and to reduce groundwater demands therein. To this end, a set of operational alternatives were investigated, including nonstructural approaches, structural modification, and automatic control systems. The potential amount of the reduction in the groundwater demands can be measured under each of the alternative operations for the delivery of water to farmers. The study is conducted on the hydrodynamic model of an irrigation canal affected by 20–70 % inflow fluctuations, which occur due to water shortages at the head source. The results of the operational simulation indicate that appropriate management of the water delivery systems within non-structural alternatives can lead to a 2–13 % improvement in operational performance indicators in comparison with the structural modification. Accordingly, the application of non-structural approaches can potentially decrease the groundwater demand by 5.352 and 8.428 Million Cubic Metres (MCM) from deep tube-wells and 2.817 and 2.007 MCM from the semi-deep tube-wells over the period of one water year. However, when employing automatic control systems, operational services to the users undergo a 15–62 % enhancement such that groundwater demand drops by 11.561 and 20.39 MCM per year, respectively.

Estimation of soil surface water contents for intertidal mudflats using a near-infrared long-range terrestrial laser scanner

Estimations of the soil surface water contents and distributions play a key role in the ecological, environmental, and topographical investigations for intertidal mudflats. However, existing techniques have limitations. Long-range terrestrial laser scanners (TLSs) can record the co-located intensity value which refers to a measure of the backscattered laser from each scanned point. Most long-range TLSs emit near-infrared lasers that can be strongly absorbed by water. Thus, the intensity values can be used as proxies for water contents. In this study, the intensity data of long-range TLSs are corrected for the incidence angle and distance effects to quantitatively estimate the soil surface water contents of intertidal mudflats. A case study for a mudflat in Chongming Island, Shanghai, China, is conducted. Results indicate that compared with traditional techniques, the corrected intensity data of long-range TLSs are extremely effective data sources for a quick, accurate, and detailed estimation of water contents for large-area mudflats. The estimation root mean square error is approximately 3%. Furthermore, the 3D distributions of the water contents can be accurately mapped by combining the point cloud of the mudflats to potentially analyze the intrinsic association among water contents and topography, vegetation coverage, and habitation of creatures in mudflats.