Groundwater Evaporation Research Articles

Distribution and Enrichment Factors of High-Arsenic Groundwater in Inland Arid Area of P. R. China: A Case Study of the Shihezi Area, Xinjiang

To study the distribution, sources and enrichment factors of groundwater As in the Shihezi area in Xinjiang, China, 19 indexes in 23 groundwater samples were tested and analyzed with a control area of 1611 km2. Results showed that As concentrations ranged between non-detected and 49.1 μg/L with an average of 11.0 μg/L. Among all the samples, 34.8% of which had As concentrations greater than 10 μg/L, according to “Standards for Drinking Water Quality (GB5749-2006)”. Groundwater As showed a significant spatial distribution. High-As groundwaters (>10 μg/L) were mainly distributed in the confined groundwater in the northern part of the study area. Arsenic concentrations in the deep confined groundwater were higher than that in the shallow confined groundwater due to mixed exploitation of groundwater in confined groundwater region and overexploitation of deep groundwater in the Shihezi area. The hydrogeochemical type of groundwater changed from HCO3·SO4–Ca·Na in the southern piedmont zone to HCO3·SO4–Na in the northern fine soil plain. High-As groundwater generally occurred under weakly alkaline and reducing conditions with dominant hydrogeochemical type of groundwater of HCO3·SO4–Na. Groundwater As mainly derived from As-containing minerals in the coal seam of the southern mountain and the extensive use of As-containing pesticides in agricultural areas. Enrichment of groundwater As was mainly influenced by climate, geological settings and hydrogeochemical characteristic. In the transition zone of oasis and desert in the north of study area, intensive evaporation of groundwater promoted the enrichment of As in shallow groundwater. In the confined groundwater area in the northern part of the study area, relatively weak groundwater runoff and reducing environment may contribute to groundwater As enrichment in confined aquifers. In addition, high pH values and high F− concentrations in the groundwater may contribute to the enrichment of groundwater As, while TDS, total Fe and Mn concentrations of groundwater had little effect on As enrichment in the study area. Two confined groundwater flow paths were selected in the study area. Inverse geochemical modeling was performed using PHREEQC. The results showed that As-containing realgar dissolved in groundwater, indicating that realgar was the major mineral source of groundwater As. The dissolved amount of realgar along deep confined groundwater flow path was higher than that along shallow confined groundwater flow path, indicating that the concentrations of As dissolved in deep confined groundwater were higher than that in shallow confined groundwater. Meanwhile, dissolution of fluorite in groundwater caused the increase in groundwater F−, which further confirmed that groundwater As and F− had a positive correlation.

Rates and geochemical processes of soil and salt crust formation in Salars of the Atacama Desert, Chile

The hyperarid Atacama Desert contains numerous local basins with surficial salt crusts, known as salars, where evaporation of shallow groundwater drives the major soil processes. We examine chemical and isotopic profiles in two soils of differing ages from the Salar Llamara to determine the geochemical processes involved in their formation. Evaporation, which provides salts to the soils through mineral precipitation, decreases with increasing salt crust thickness, and average~0.03mmm−2d−1 over geological time frames. Salt distribution varies predictably with depth and soil age, with the most soluble compounds concentrated nearest to the land surface, indicating the direction of fluid flow. δ34S values of mineral sulfate tend to decrease with decreasing soil depth, following a pattern indicative of Rayleigh-like fractionation as solute-rich waters migrate toward the land surface. δ13C and δ18O values of carbonate suggest that the uppermost halite layers, which contain very small amounts of carbonate, have a strong biological signature. In contrast, carbonate-rich layers deeper in the profiles consist of largely unmodified lacustrine carbonate that formed in highly evaporitic lake conditions. The continuous upward evaporation of water and dissolved solutes creates a rugged and physically dynamic halite crust composed of rounded salt nodules. The crust undergoes deliquescence as atmospheric relative humidity rises from marine air intrusions, and we found that the halite nodules on the surface of the Salar Llamara are nearly always at or above deliquescence relative humidity. The interiors of these nodules are therefore able to buffer the large diurnal changes in atmospheric relative humidity allowing for the survival of halophilic microbial communities in an otherwise very dry environment. Radiocarbon measurements of occluded organic C in the surface crusts indicate that C cycling occurs at differing rates depending on local micrometeorological conditions, and that a given salt crust feature may persist for thousands of years once formed.

Groundwater Evaporation Ponds: A Viable Option for the Management of Shallow Saline Waterlogged Areas

The province of Punjab is the main food basket of India. In recent years, many regions of Punjab are facing acute waterlogging problems and increased secondary salinity, which have negative impacts on food security of the nation. In particular, these problems are more pronounced in the Muktsar district of Punjab. The observed groundwater levels trend between 2005 and 2011 implies that groundwater levels are coming towards the land surface at the rate of 0.5 m/year in Lambi and Malout blocks. In this study, a groundwater flow model was constructed using MODFLOW to understand the groundwater table dynamics and to test the groundwater evaporation ponds to draw down the groundwater levels in the waterlogging areas of Muktsar district. The predicted flow model results indicate that groundwater levels could be depleted at the rate of 0.3 m/year between 2012 and 2018 after the construction of Groundwater Evaporation Ponds (GEP). In addition, the constructed ponds can be used for aquaculture that generates additional income. The proposed GEP method may be a promising tool and suitable for the reduction of waterlogging in any region if there is no proper surface drainage, and also for enhancement of agricultural production that improves the social and economic status of the farming community.

Impacts of agricultural water saving practice on regional groundwater and water consumption in an arid region with shallow groundwater

Irrigation is important to agricultural production and can induce changes in the regional hydrological cycle. In particular, in areas with shallow groundwater, fluctuation of groundwater levels will be present with irrigation events and groundwater evaporation. To deal with the shortage of water resources, agricultural water saving (AWS) has been conducted in arid and semiarid area. The Jiefangzha irrigation district was selected as the study area to investigate groundwater dynamics in response to AWS. With the abundant various data, the trend of groundwater level change from 1980 to 2013 was evaluated based on geographic information systems. Groundwater net consumption (ETng) and regional evapotranspiration (ET) during crop growth period were estimated by water fluctuation method and the water balance method. The results indicate that the groundwater depth was relatively stable before 2002, remaining at around 1.7 m. Due to reduction of the water diversion from the Yellow River and the implementation of water saving measures (WSMs), the canal seepage and irrigation infiltration declined, leading to groundwater levels declining by 0.4 m in recent 10 years. Groundwater net consumption of crop growth period was estimated since 1990 and increased from 50 mm/year in 1990 to 110 mm/year in 2013 with the reduction of water diversion. At the same time, regional evapotranspiration has shown a slightly decreasing trend. Thus, the contribution of groundwater to regional evapotranspiration has an obvious increasing trend, accounting for 20 % in 2013, which is doubled compared with that in 1980. Groundwater is very important to sustain crop production and healthy ecology, and it is quite essential to consider groundwater response to regional WSMs and water management.

A framework for sourcing of evaporation between saturated and unsaturated zone in bare soil condition

ABSTRACTSourcing subsurface evaporation (Ess) into groundwater (Eg) and unsaturated zone (Eu) components has received little scientific attention so far, despite its importance in water management and agriculture. We propose a novel sourcing framework, with its implementation in dedicated post-processing software called SOURCE (used along with the HYDRUS1D model), to study evaporation sourcing dynamics, define quantitatively “shallow” and “deep” water table conditions and test the applicability of water table fluctuation (WTF) and “bucket” methods for estimation of Eg and Eu separately.For the “shallow” and “deep” water table we propose Eg > 0.95Ess and Eg = 0 criteria, respectively. Assessment of the WTF method allowed sourcing of very small fluxes otherwise neglected by standard hydrological methods. Sourcing with SOURCE software was more accurate than the standard “bucket” method mainly because of greater flexibility in spatio-temporal discretization. This study emphasized the dry condition relevance of groundwater evaporation which should be analysed by applying coupled flow of heat, vapour and liquid water.Editor D. Koutsoyiannis; Associate editor S. Kanae

Regimes of haline convection during the evaporation of groundwater containing a dissolved admixture

The problem of formation of salt concentration profile in high-permeability soil duringwater evaporation and solution upflow is considered. The numerical experiments performed showed that the salt concentration profile may be either stable or unstable. As instability develops, there arises natural haline convection whose different regimes are described and analyzed. If the evaporation intensity is moderate, in soil the curvilinear upward or circulatory flow that fills the entire layer is established. The intense evaporation leads to the formation of a small-scale structure of salt “fingers”. Boundaries between regimes are determined.

Impacts of water saving on groundwater balance in a large-scale arid irrigation district, Northwest China

Water saving practices are essential for sustainable use of water resources in semiarid regions. To understand the impacts of different water saving measures on groundwater resources, the Hetao Irrigation District in Northwest China was chosen in this study. Based on the data from 1991 to 2010, a groundwater balance model was calibrated and validated. The simulation results showed that irrigation-induced infiltration (92 % of the total groundwater recharge) and groundwater evaporation (92 % of the total groundwater discharge) were the primary factors controlling groundwater table fluctuations during irrigation seasons. The impacts of different water saving scenarios on groundwater balance components were then evaluated. The results revealed that the conjunctive use of water resources was the most effective way to improve water use efficiency (reducing surface water diversions by 52 %) and the depth to groundwater table increased by up to 79 cm. However, deeper groundwater tables may have a negative effect on crop growth due to reduced upward fluxes of groundwater into root zones. Therefore, future studies are needed to evaluate the impacts of different water saving measures on both water resources and crop yields. The results of this study provide further insights into effectively managing water resources in water-limited agricultural areas.

Appraising Groundwater Quality and Health Risks from Contamination in a Semiarid Region of Northwest China

This study assessed groundwater quality in a semiarid region of northwest China impacted by industrial and agricultural activities. The goal was to assess the quality of the water for drinking and irrigation, and the groundwater’s effect on human health. Thirty-one groundwater samples were collected from monitoring and hand pumping wells. These wells were distributed over 54 km2, with an average of 5.7 wells per 10 square kilometers. The samples were analyzed for pH, total dissolved solids (TDS), total hardness (TH), fluoride (F−), nitrate (NO3–N), nitrite (NO2–N), ammonia nitrogen (NH4–N), major ions (Na+, K+, Ca2+, Mg2+, HCO3 −, SO4 2−, Cl−), and heavy metals (Cu, Mn, Zn, As and Cr6+). Groundwater chemistry was described using statistical analysis, and Piper and Gibbs diagrams. An entropy-based matter element extension analysis was performed to quantify the overall groundwater quality. The sodium adsorption ratio, residual sodium carbonate, and soluble sodium percentage were used to assess irrigation water quality. Considering resident age, sex, and exposure pathways, the non-carcinogenic and carcinogenic health risks were estimated using the models recommended by the Ministry of Environmental Protection of China. Study area groundwater was found to be slightly alkaline. For cations, Na+ was most abundant followed by Ca2+, then Mg2+, and then K+. For anions, HCO3 − were more abundant than SO4 2− and Cl−. Gibbs diagrams indicate that groundwater evaporation influences the development of sulfate-type groundwater, compared to the other groundwater types (bicarbonate and non-dominant types). The groundwater in most parts of the study area is of fair quality, and is marginally acceptable for multiple uses. TDS, TH, NH4−N, NO3−N, and Mn are common contaminants in the alluvial plain. These contaminants originate mainly from industrial and agricultural activities, as well as natural processes. Land irrigated with the groundwater is not exposed to a sodium hazard. However, measures are needed to manage the salinity hazard. The health risk assessment suggests that females and children face higher non-carcinogenic risk than males. The contribution of the contaminants to non-carcinogenic risk is in the following order: NO3 −> F−> As > Mn > NO2 −> Cr > NH4 +> Cu > Zn. Cr contributes more than As to the carcinogenic risk.

Hydrogeochemical Characterization of Groundwater in and Around a Wastewater Irrigated Forest in the Southeastern Edge of the Tengger Desert, Northwest China

Groundwater is an essential part of water resources for human survival and economic development in arid regions over the world. Human activities and environmental change have imposed significant impacts on groundwater environment. To investigate the hydrogeochemical characteristics and evolution of groundwater in and around a desert region impacted by wastewater irrigation, 84 groundwater samples were collected and analyzed for 18 indices. Statistical and graphical approaches were applied to delineate the general hydrochemical characteristics of groundwater and the major factors influencing its evolution. Stable isotopes of 2H and 18O were applied to identify groundwater evaporation process. Hydrogeochemical modeling was also adopted to quantify the major reactions occurring in the groundwater system. The results reveal that the abundance of cations is Na+ > Ca2+ > Mg2+ > K+ for groundwater in the entire study area, while the abundance of anions for groundwater in the desert region is HCO3 − > Cl− > SO4 2−, and that for groundwater in the alluvial plain is HCO3 − > SO4 2− > Cl−. Groundwater chemistry in the study area is mainly of rock dominance, and dissolution/precipitation of minerals and cation exchange are major natural factors governing the formation of groundwater chemistry. However, stable isotopes and the occurrence of nitrate show that shallow groundwater evaporation and human activities also have some impacts on groundwater quality. Hydrochemical type transits from Ca–Cl to HCO3·SO4–Ca type, and then to HCO3·SO4–Ca·Mg type along the flow path. The transition is influenced by multiple factors with water–rock interactions the predominant one. The water–rock interactions for the upper and lower sections of the flow path, indicated by hydrogeochemcial modeling, are different due to different geologic and hydrogeologic conditions.

Groundwater flow, nutrient, and stable isotope dynamics in the parafluvial-hyporheic zone of the regulated Lower Colorado River (Texas, USA) over the course of a small flood

Periodic releases from an upstream dam cause rapid stage fluctuations in the Lower Colorado River near Austin, Texas, USA. These daily pulses modulate fluid exchange and residence times in the hyporheic zone where biogeochemical reactions are typically pronounced. The effects of a small flood pulse under low-flow conditions on surface-water/groundwater exchange and biogeochemical processes were studied by monitoring and sampling from two dense transects of wells perpendicular to the river. The first transect recorded water levels and the second transect was used for water sample collection at three depths. Samples were collected from 12 wells every 2 h over a 24-h period which had a 16-cm flood pulse. Analyses included nutrients, carbon, major ions, and stable isotopes of water. The relatively small flood pulse did not cause significant mixing in the parafluvial zone. Under these conditions, the river and groundwater were decoupled, showed potentially minimal mixing at the interface, and did not exhibit any discernible denitrification of river-borne nitrate. The chemical patterns observed in the parafluvial zone can be explained by evaporation of groundwater with little mixing with river water. Thus, large pulses may be necessary in order for substantial hyporheic mixing and exchange to occur. The large regulated river under a low-flow and small flood pulse regime functioned mainly as a gaining river with little hydrologic connectivity beyond a narrow hyporheic zone.

Coupled thermal-hydrological-mechanical behavior of rock mass surrounding a high-temperature thermal energy storage cavern at shallow depth

We numerically model the thermal-hydrological-mechanical (THM) processes within the rock mass surrounding a cavern used for thermal energy storage (TES). We consider a cylindrical rock cavern with a height of 50m and a radius of 10m storing thermal energy of 350°C as a conceptual TES model, and simulate its operation for thirty years. At first, the insulator performance are not considered for the purpose of investigating the possible coupled THM behavior of the surrounding rock mass; then, the effects of an insulator are examined for different insulator thicknesses. The key concerns are hydro-thermal multiphase flow and heat transport in the rock mass around the thermal storage cavern, the effect of evaporation of rock mass, thermal impact on near the ground surface and the mechanical behavior of the surrounding rock mass. It is shown that the rock temperature around the cavern rapidly increases in the early stage and, consequently, evaporation of groundwater occurs, raising the fluid pressure. However, evaporation and multiphase flow does not have a significant effect on the heat transfer and mechanical behavior in spite of the high-temperature (350°C) heat source. The simulations showed that large-scale heat flow around a cavern is expected to be conduction-dominated for a reasonable value of rock mass permeability. Thermal expansion as a result of the heating of the rock mass from the storage cavern leads to a ground surface uplift on the order of a few centimeters, and to the development of tensile stress above the storage cavern, increasing the potentials for shear and tensile failures after a few years of the operation. Finally, the analysis shows that high tangential stress in proximity of the storage cavern can some shear failure and local damage, although large rock wall failure could likely be controlled with appropriate insulators and reinforcement.

Hydrochemical appraisal of groundwater quality for drinking and irrigation purposes and the major influencing factors: a case study in and around Hua County, China

Groundwater is the major source of water for drinking and irrigation purposes in and around Hua County, China. However, long-term industrial effluents in the upstream of the area have produced contamination to groundwater. To provide a clear and better understanding of the status and extent of groundwater pollution to local decision makers, groundwater quality was assessed for drinking and irrigation purposes in this study using sodium adsorption ratio (SAR), residual sodium carbonate (RSC), soluble sodium percentage (%Na), permeability index (PI), an entropy weighted water quality index (EWQI), and some graphical approaches such as Wilcox and US Salinity Laboratory (USSL) diagrams. Factors that have significant influences on the hydrochemistry and quality of groundwater were also discussed in detail. Finally, some measures for the protection and management of groundwater in the study area were provided to local decision makers. The results show that shallow groundwater in and around the Hua County is mainly slightly alkaline freshwater with the majority of the samples falling in the category of HCO3–Ca and mixed HCO3·SO4–Ca·Mg. Medium quality water is prevalent in the study area for drinking purpose, and the main contaminants in groundwater are total dissolved solid (TDS), total hardness (TH), SO4 2−, Cl−, NO3 −, NO2 −, and oil. Groundwater in the study area is suitable for agricultural irrigation with regard to sodium hazard, but mixing of low and high salinity water is recommended before irrigation to reduce the salinity hazard in local areas. Natural processes such as weathering of parent rocks, cation exchange, and groundwater evaporation are the dominant factors influencing groundwater chemistry in the study area. However, river water leakage and human interference are becoming increasingly important in altering natural groundwater chemistry. The recommendations suggest in this study may help to prevent further groundwater pollution in the study area, and the results and recommendations reported here will also be useful for many other regions facing similar problems.

Groundwater evaporation from salt pans: Examples from the eastern Arabian Peninsula

Summary The major groundwater resources of the Arabian Peninsula are stored in the large sedimentary basins in its eastern part. Evaporation from continental salt pans (playas) is an important process in water resources assessments of its upper principal aquifers – the Upper Mega Aquifer system – as it constitutes a significant sink. However, literature values on evaporation rates vary widely and usually report about coastal salt pans where seawater evaporation is assumed. The present study applies different methods to provide a comprehensive picture of groundwater evaporation from salt pans of the Upper Mega Aquifer system. A remote sensing approach provided the spatial distribution and total salt pan area of about 36,500 km 2 . Hydrochemical and isotopic investigations revealed that from about 10% (3600 km 2 ± 1600 km 2 ) of the mapped salt pan area seawater evaporates. To estimate the groundwater evaporation rate from continental salt pans a laboratory column experiment was set up, implying a mean annual evaporation rate of about 42 mm ± 13 mm. In-situ analysis of water table fluctuations in the field suggested about 3 mm a −1 originate from recently infiltrated rainwater leading to an annual net groundwater evaporation of 39 mm ± 13 mm. Relating this number to the mapped salt pan area, from which groundwater evaporates, provides a total annual groundwater loss of 1.3 km 3 ± 0.5 km 3 for the Upper Mega Aquifer system.

암반 공동 열에너지저장소 주변 암반의 수리적 조건에 따른 열-수리-역학적 연계거동 분석

The thermal-hydrological-mechanical (T-H-M) behavior of rock mass surrounding a large-scale high-temperature cavern thermal energy storage (CTES) at a shallow depth has been investigated, and the effects of hydrological conditions such as water table and rock permeability on the behavior have been examined. The liquid saturation of ground water around a storage cavern may have a small impact on the overall heat transfer and mechanical behavior of surrounding rock mass for a relatively low rock permeability of . In terms of the distributions of temperature, stress and displacement of the surrounding rock mass, the results expected from the simulation with the cavern below the water table were almost identical to that obtained from the simulation with the cavern in the unsaturated zone. The heat transfer in the rock mass with reasonable permeability was dominated by the conduction. In the simulation with rock permeability of , however, the convective heat transfer by ground-water was dominant, accompanying the upward heat flow to near-ground surface. The temperature and pressure around a storage cavern showed different distributions according to the rock permeability, as a result of the complex coupled processes such as the heat transfer by multi-phase flow and the evaporation of ground-water.

Ce(III) and Ce(IV) (re)distribution and fractionation in a laterite profile from Madagascar: Insights from in situ XANES spectroscopy at the Ce LIII-edge

The distribution of trivalent and tetravalent cerium, Ce(III) and Ce(IV) respectively, in a lateritic profile from Madagascar, has been characterized by X-ray-absorption near-edge structure (XANES) spectroscopy at the Ce LIII-edge on the LUCIA beamline (SOLEIL synchrotron, France). XANES spectra were acquired on bulk-rock samples as well as on specific lateritic minerals or polymineral zones (in-situ measurements) of the tonalite bedrock and the three overlying weathered horizons (C-, B- and A-horizons). Geochemically, the bedrock, and the A- and C-horizons show similar rare earth element content (REE=363–405mg/kg). They also display the same positive Ce-anomaly (CeCN/Ce∗=1.12–1.45), which is therefore likely to be inherited from the bedrock. In the B-horizon, the higher REE content (REE=2194mg/kg) and the larger Ce-anomaly (CeCN/Ce∗=4.26) are consistent with an accumulation zone caused by the evaporation of groundwater during the dry season. There is a good agreement between the Ce(III)/Cetotal ratio (XCe(III)) deduced from the positive Ce-anomaly (bulk-rock geochemical data) and that derived from XANES spectroscopy on the same bulk-rock samples (BR-XCe(III)-XANES) in the bedrock, and the C- and B-horizons. In the A-horizon, XANES measurements on bulk rock and minerals revealed a higher BR-XCe(III)-XANES (up to 100%) compared to the XCe(III) deduced from geochemical data (XCe(III)=79%). The preservation of a positive Ce-anomaly in the A-horizon suggests that the Ce mobilization and redistribution during weathering occurred with no significant Ce fractionation from other trivalent REE. Remarkably, the only investigated sample where cerianite is observed belongs to the B-horizon. Within this horizon, Ce oxidation state varies depending on the microstructural position (porosity, cracks, clay-rich groundmass). The highest Ce(IV) concentrations are measured in cerianite (and aluminophosphates) localized in pores at the vicinity of Mn-rich domains (XCe(III)-XANES=30–51%). Therefore, Ce fractionation from other REE is attributed to a Ce oxidation and precipitation potentially assisted by oxyhydroxide scavenging. In the C-horizon, Ce(III) and Ce(IV) are mainly distributed in REE-minerals of the rhabdophane group found in pores and cracks. The similarity between the Ce(III) proportion of rhabdophane grains (XCe(III)-XANES=74–89%) with that of the bedrock (BR-XCe(III)-XANES=79%) suggests no significant fractionation of Ce(III) and Ce(IV) between solution and mineral during the successive stages of primary REE-mineral alteration, transport in solution and secondary precipitation in the incipient stages of weathering. Overall, our novel spectroscopic approach shows that Ce is not necessarily oxidized nor fractionated from other REE during weathering in lateritic conditions. This implies that like Ce(III), Ce(IV) can be mobilized in aqueous fluids during weathering, possibly thanks to complexation with organic molecules, and can precipitate together with Ce(III) in secondary REE-bearing minerals. The corollary is that (paleo)redox reconstructions in soils and/or sediments based on Ce-anomaly in weathered rocks or minerals must be interpreted with caution.

Study on extinction depth and steady water storage in root zone based on lysimeter experiment and HYDRUS-1D simulation

HYDRUS-1D was combined with lysimeter experiments to study extinction depth and steady water storage in root zone (Ws) of groundwater evaporation (ETgw) under winter wheat and silt soil. The measured soil water contents and daily ETgw with various groundwater depths were used to calibrate and validate the parameters in HYDRUS-1D. In total, 13 groundwater depths ranging from 0.5 to 5.0 m were set up for scenario simulation to determine the extinction depth and Ws. The results showed that HYDRUS-1D had an acceptable performance in simulating the soil water storage in the 0–60 cm layer and the daily ETgw. Moreover, the ETgw decreased linearly with increasing groundwater depth from 0.5 to 2.5 m and decreased as a power function with increasing groundwater depth from 2.5 to 5.0 m. Under the condition of winter wheat and silt soil, the extinction depth of ETgw was about 5.0 m. Ws decreased linearly with increasing groundwater depth from 0.7 to 2.0 m, but was not influenced further by the groundwater at depths beyond 2.0 m.

Simulation of groundwater evaporation and groundwater depth using SWAT in the irrigation district with shallow water table

In irrigation districts with shallow water table, groundwater evaporation (ETgw) and groundwater depth are important variables for the study of water balance. These variables are influenced by natural factors and human activity. In this study, a new method of simulating ETgw was used for SWAT, and the computing and output modules of groundwater depth were established. In addition, based on simulations, we analyzed the influences of irrigation schedules and soil types on ETgw and groundwater depth in the Irrigation Districts along the Lower Reach of Yellow River Basin. The applicabilities of the three methods (Hargreaves, Priestley-Taylor and Penman-Monteith) simulating potential evapotranspiration in SWAT 2000 were evaluated by the measured groundwater evaporation, and Hargreaves was applied in the simulation for irrigation district due to its smallest simulation error. The results presented that the mean groundwater depth decreased with the increase of irrigation amount. However, the changes of soil water storage in root zone and groundwater depth might have more complex effects on the variation of the mean groundwater evaporation. Loamy sand had the smallest annual mean groundwater depth and mean annual ETgw in the study area, while silt loam corresponded to the largest groundwater depth and groundwater evaporation. This study provides a new method for making simulations and analyses of the hydrological cycle in irrigation districts which has a shallow water table.

Quantifying bare soil evaporation and its relationship with groundwater depth

The spatial variation of evapotranspiration (ET) and its relationship with vegetation and groundwater depth in the arid Yinchuan plain of China was studied by combining remote-sensing data with groundwater depth observation. The vegetation cover was quantified with the normalized difference vegetation index (NDVI), ET was estimated with the surface energy balance system, and the groundwater depths were measured in monitoring wells. The results show that an area of the plain is covered by vegetation when the NDVI of the area is larger than 0.2 and that groundwater depth is an important factor influencing the ET in the arid region: the deeper the groundwater, the less the ET. The threshold depth of groundwater evaporation is 4 m in the rainy season. A method of quantifying soil evaporation at a regional scale was also presented in this study. The results obtained in this study are useful for future study of the regional water cycle and climate.

A new type of jarosite deposit on Mars: Evidence for past glaciation in Valles Marineris?

Acid-sulfate minerals such as jarosite are often used as indicators of environmental conditions on Mars. These minerals form in a diverse set of environments on Earth; however, all known Martian jarosite deposits are most likely evaporative, from evaporation of either groundwater or ponded water. Here, we use the Compact Reconnaissance Imaging Spectrometer for Mars and High-Resolution Imaging Science Experiment to report a new jarosite deposit along the southern wall of Ius Chasma. The morphology and geologic context of the Ius deposit are unique on Mars, and difficult to explain with an evaporative or groundwater mechanism. We propose instead that it was deposited along the margins of a past glacier. Such acid-ice interactions would be similar to those reported along the margins of Svalbard glaciers (arctic Norway), and would represent a new style of acid-sulfate formation on Mars.

Effect of ignoring parameter b on the maximum upward flux calculated from the Gardner rational model

Shi, W.-J., Shen, B. and Wang, Q.-J. 2014. Effect of ignoring parameter b on the maximum upward flux calculated from the Gardner rational model. Can. J. Soil Sci. 94: 97–103. The maximum upward flux (E max) of groundwater evaporation can be predicted using the Gardner model. The model is often simplified by neglecting a soil parameter (b). The paper describes methods used to assess the impact of the b parameter on predictions of E max including or eliminating b in the Gardner model. The results showed that ignoring b always resulted in a higher prediction of E max; for the same soil, the calculated E max ignoring b was higher than E bmax including b, and the difference between the measured E max and calculated E bmax was smaller. For different soils, the difference between predicted E max ignoring b and measured value increased as the soil mean particle size increased (when the water table depth was more than 1 cm). For layered soils, the measured E max was always smaller than the calculated value, regard...