Changes In Water Volume Research Articles

Lake and reservoir volume variations in South America from radar altimetry, ICESat laser altimetry, and GRACE time-variable gravity

Thanks to 25-years of radar altimetry measurements from TOPEX/POSEIDON, Jason 1, 2 and 3, ENVISAT and others, water level changes of major lakes and rivers can be measured regularly, remotely, with unprecedented precision, facilitating monitoring of continental water storage variations. In addition, the 18 laser altimeter measurement campaigns over 6 years by the Ice, Cloud and Land Elevation Satellite (ICESat) satellite complement these radar altimetry measurements and also validate them, expanding our monitoring capabilities. We extract derived water height estimates for various lakes in South America from radar and laser altimetry measurements. Using available imagery from the Moderate Resolution Imaging Spectroradiometer (MODIS), we estimate time-variable surface extent of these water bodies, and together with the altimetry, we derive corresponding estimates of relative volume variations for a number of lakes and reservoirs in South America. We see good agreement between our water extent and available products, with some differences when snow covered area are present. We find good agreement between the temporal variations of lake water heights obtained from ICESat, radar altimetry, and in situ measurements, when available. Lake-dependent biases still exist, likely due to differences in reference datum, choice of geoid model, and differences in data processing schemes. The is a good agreement in volume changes obtained from imagery and the various altimetry techniques. Furthermore, using the latest one-degree global iterated mascon solutions from NASA Goddard Space Flight Center, we successfully compare them to independent volume changes assessments for these water bodies, derived from mass variations from time-variable gravity measurements from 15 years of Gravity Recovery And Climate Experiment (GRACE) observations. The agreement in water volume changes from GRACE with those from altimetry and imagery is higher for lakes in arid and semi-arid regions than on mountainous areas. GRACE volume estimates remain limited to the spatial resolution and the quality of the hydrology models used to correct for soil-moisture and snow contributions. Overall, studies like the one presented here further validate the power of leveraging these data synergies to monitor continental water storage changes from space, taking advantage of what each of the techniques has to offer. We show that water level measurements from laser and radar altimeters have similar precision, of a few centimeters over inland water bodies, and prove that GRACE global mascons allow to retrieve small lake relative volume changes, even for small bodies, thanks to their higher sensitivity to small wavelength mass variations.

Interseeding alfalfa into native grassland for enhanced yield and water use efficiency

AbstractLivestock productivity of semiarid, native grassland is potentially enhanced by interseeding alfalfa (Medicago sativa L.), but little is known of the impact on forage and N yield and water use. Two hay‐type cultivars, ‘WL 440HQ’ (WL), ‘NuMex Bill Melton’ (NuMex), and grazing‐type ‘Falcata’–‘Rhizoma’ blend (FR) were interseeded into mixtures of four native‐grass species in fall of 2015, at 36‐ and 71‐cm row spacing as high‐ and low‐density plantings, respectively. Plots were harvested periodically over 3 yr. Evapotranspiration (ET) was estimated based on rainfall and changes in soil water volume and used to calculate water use efficiency (WUE, kg of forage mass m−3 of ET). Alfalfa–grass mixtures produced 35% more forage mass and 96% greater N yield than the grass‐only stands. Narrow‐row alfalfa produced greater total forage mass than wide‐row for the first 2 yr (P < .05), but no difference between row spacings occurred by Year 3. Cultivars NuMex and WL produced greater forage mass than the short‐statured FR, especially at high density (P < .05). Alfalfa–grass mixtures increased WUE by a mean of 25% over the grass‐only stands. There was no difference between row spacings for WUE, weed biomass, and weed N mass (P > .05). The alfalfa–grass mixtures reduced weed biomass by 43% over the grass‐only stands. Interseeding alfalfa at wide row spacing enhanced forage productivity, WUE, and weed suppression relative to grass‐only stands at lower seed cost than at narrow row spacing. Adapted hay‐type alfalfa cultivars can be used to improve native‐grass pastures in rainfed, semiarid environments.

Changes in area and water volume of the Aral Sea in the arid Central Asia over the period of 1960–2018 and their causes

The Aral Sea (68,478 km2 in 1960) was the world’s fourth largest inland lake in 1960s. However, it shrank sharply over the past six decades, and its changes caused a series of severe environmental issues. In this paper, we reconstructed its variations over the period of 1960 to 2018 by using observation data and remote sensing data, and analyzed their influencing factors. The results show that the area of the Aral Sea shrank dramatically by 60,156.50 km2 (about 87.85%) and the total loss of water volume was approximately 1,000.51 km3 over the study period. In 1986, the Aral Sea broken up into the south and the north parts. Since then, the South Aral Sea has shrunk continuously, while both the area and the water volume of the North Aral Sea have had a little change and shown a very slightly increasing trend. Through comprehensive analysis, it was found that human activities, especially damming and irrigation, are the dominant factors influencing the long-term variation of the Aral Sea. The increased precipitation and glacier meltwater could not compensate for the water loss of the Aral Sea.

THE INFLUENCE OF THE USE OF RECYCLED GYPSUM ON THE PROPERTIES OF GYPSUM PRODUCTS IN LABOR CONDITIONS

The article presents the first results from research, which is deal with recycling of plaster boards and use of the resulting material. The research is carried out within the project MPO Trio c. FV30359 “Recyklace sádrokartonových desek a nová materiálová využití s pridanou hodnotou – GIPSRec”. The plasterboards are produced of stucco, which is calcinated of Flue Gas Desulfurization Gypsum (FGD Gypsum). There is possibility to replace a part of this stucco with recycled material. There is opportunity for saving costs for production. The question how this utilization can change the properties of the products is very important and it is necessary to find the possible improvement or deterioration. This is the objective of this research. The effect on properties was monitored on the samples which was prepared of only pure stucco and of stucco with part of recycled material. There was observed water ratio (splash test), setting times, volume changes, flexural strength, compressive strength and elasticity module.

Effects of water content, water type and temperature on the rheological behaviour of slag-cement and fly ash-cement paste backfill

The pumping ability and placement performance of fresh cemented paste backfill (CPB) in underground mined cavities depend on its rheological properties. Hence, it is crucial to understand the rheology of fresh CPB slurry, which is related to CPB mixture design and the temperature underground. This paper presented an experimental study investigating the effects of binder type, content, water chemical properties and content, and temperature, on the rheological properties of CPB material prepared using the tailings of a copper mine in South Australia. Portland cement (PC), a newly released commercially manufactured cement called Minecem (MC) and fly ash (FA) were used as the binders added to the mine tailing materials. Various amounts of two different water types were added to the mixtures in the preparation of backfill material slurry. Six different temperatures ranging from 5 to 60 °C were to investigate the effect of temperature on CPB rheology. Overall, the increasing water content and decreasing temperature lead to lower yield stress. Based on the results obtained from the rheological properties of CPB slurry, it was found that at room temperature (25 °C), with regards to the unconfined compressive strength (UCS) performance, the replacement of 4% PC mixed CPB (28 days UCS 425 kPa) to 3% MC mixed CPB (28 days UCS 519 kPa), reduced the slurry yield stress from 210.7 to 178.5 Pa. The results also showed that the chemical composition of water affects the yield stress of CPB slurry and that MC mitigates the negative effect of mine-processed water (MW) and thus lead to improve the rheological properties of the slurry. However, the results suggested that the rheological properties of a mixture using MC is very sensitive to the water volume and temperature change. Therefore, using MC in backfill requires better quality control in slump mixing.

Determinants of Eurasian otter (Lutra lutra) diet in a seasonally changing reservoir

Otter diet in reservoirs is known to experience seasonal changes. We selected a reservoir with a large population of exclusively wintering great cormorants and seasonal changes in stored water volume to test the relative influence of abiotic and biotic factors on otter foraging ecology. DNA metabarcoding of otter spraints revealed a dietary change from autumn to winter. Otters had a diet dominated by the exotic goldfish in autumn, but predated intensively on the native northern straight-mouth nase in winter. This change was likely caused by predation of cormorants on goldfish and to fish biology. Secondly, macroscopic analysis of spraints revealed that otters shifted from a diet dominated by fish (in terms of biomass) to a diet dominated by red swamp crayfish during spring–summer, when the latter became overabundant. As revealed by modelling, this second shift was most likely influenced by the sudden increase in stored water volume in spring, but also by the cumulative effect of cormorant predation on fish during autumn–winter. Macroscopic analyses of otter spraints collected in a second reservoir with no cormorants revealed a lack of seasonality. Hence, the combined influence of both biotic and abiotic factors explained otter diet seasonality in a lentic-water novel ecosystem.

A Suction-Controlled Ring Device to Measure the Coefficient of Lateral Soil Pressure in Unsaturated Soils

A suction-controlled ring device has been developed to continuously measure the coefficient of lateral soil pressure in deformable unsaturated soil samples from the at-rest to the active condition under application of increasing vertical pressure and controlled matric suction. The device incorporates a thin aluminum specimen ring equipped with horizontal strain gages for recording the lateral soil strains. In addition, a sensor recording water volume changes is utilized to continuously monitor the degree of saturation of the soil sample during tests. The matric suction within the soil texture is controlled using the axis translation technique. In order to verify the performance of the ring device, twenty suction-controlled tests under application of five different constant matric suctions have been performed on two different unsaturated soil types, namely Firouzkouh Clay and Sand-Kaolin mixture, each with two different initial densities. During tests, the lateral soil pressure and corresponding lateral strains have been continuously recorded from the at-rest to the active state of the soil. Accordingly, the coefficients of the lateral soil pressure for the at-rest and the active states of the soil are calculated based on the experimental data and by considering the effective stress concept in unsaturated soils. Finally, the observed responses have been analyzed and the effects of initial density and matric suction on the ratio of lateral to vertical soil pressure have been discussed.

Coupled chemo-hydro-mechanical effects in one-dimensional accretion of cemented mine fills

Mine waste-cement mixtures have been extensively used for filling underground mined-out cavities worldwide as a sustainable solution to tailings disposal and for ground control. The pressure that a mine fill imposes on its retaining structures would dictate the stability of a subsurface backfill system. The pressure is influenced by the coupled consolidation and chemical shrinkage processes of a cemented mine fill. Various benchmark results have become available for understanding and predicting such coupled processes during the deposition of cemented mine fills in an ideal one-dimensional (1D) condition. Nevertheless, there has been a paucity of studies where the coupled chemo-hydro-mechanical effects in their entirety are rationally considered. In this paper, the coupled chemo-hydro-mechanical behaviour of fluid-saturated cemented mine fills during 1D accretion is investigated with a new chemo-poroelasticity framework. The present approach is conceptualized by extending Biot's poroelasticity to accommodate the water volume changes induced by cement hydration. The analyses performed in the study have brought new practical insights into the chemo-poromechanical behaviour of accreting cemented mine fills. In particular, the study has shown quantitatively for the first time how the consolidation of a hydrating mine fill is dictated by the specific evolution of its properties, rate of deposition, as well as backfill mix design during sedimentation. The study suggests that a case-specific analysis with coupled numerical tools, rather than the simple application of benchmark results, is mandatory for rationally assessing the nonlinear consolidation process.

Water volume differentially modifies copepod predatory strengths on two prey types

Predatory interaction strengths are highly context-dependent, and in temporary aquatic ecosystems, may be affected by water volume changes. We examine the influence of water volume on Lovenula raynerae (Copepoda) functional responses towards two temporary pond prey types. Daphnia prey risk was not affected by increasing water volume, whereas for Culex prey risk was reduced. Accordingly, water volume changes through the hydroperiod may have species-specific effects on prey, with implications for population persistence under environmental change.

The intracellular water volume modulates the accumulation of cadmium in Euglena gracilis

In order to describe a relatively novel mechanism associated to heavy metal resistance in Euglena gracilis, the osmotic responses during cadmium accumulation were analyzed. Several physiological/biochemical parameters were assessed in E. gracilis exposed to 50 and 200 μM Cd2+, concentrations well within the range found in polluted soils and aquatic environments. The Cd2+ accumulation attained after only 24 h exposure induced marked increases in both the intracellular water volume and cellular size, which were maintained for several days; these changes correlated with (i) an increased intracellular osmolarity (i.e. osmotic pressure) driven by a generalized increase in the osmo-metabolites (trehalose, phosphate-molecules, amino acids, thiol-molecules, betaines and polyamines) content; and (ii) the triggering of antioxidant defenses (increased GSH/GSSG ratios and GPx, GR and APx activities). In contrast, no changes in intracellular volume, cellular size and antioxidant status were observed under hyperaccumulation of Zn2+. Furthermore, E. gracilis cultured in a hypoosmotic medium promoted greater Cd2+ accumulation and water volume, compared to a hyperosmotic medium. These changes were significantly decreased by the aquaporin inhibitors Hg2+ and pentamidine. The results suggested that the cell responses to Cd2+ and osmotic stress share biochemical mechanisms in this algae-like protist, in which Cd2+ accumulation closely correlates with the intracellular water volume changes in an oxidative stress-mediated process.

Effect of Post-Added Water Amount on Pre-Concentrated Bark Foaming Materials by Mechanical Stirring

In this study, pre-concentrated bark, furfuryl alcohol and other biomass raw materials were used to prepare foaming materials by high-speed mechanical stirring without using a foaming agent. We investigated the effect of the postadded water amount on the properties of foaming materials. In particular, we determined basic physical properties of these materials, including the limiting oxygen index (LOI), porosity, thermal conductivity, thermogravimetric analysis, pore size distribution, and microstructure. The results of scanning electron microscopy (SEM) indicated that the pore size distribution was uniform and the pore size increased with increasing water volume. Thermogravimetric analysis (TG/ DTG) showed that when the temperature reached 410°C, the foam was easily decomposed, the final residual mass was only 2.8%, and water addition had little effect on it. Moreover, the amount of post-added water is 5–30 g, the density and compression strength of the foamed materials gradually decreased, while the degree of pulverization increased. LOI ranged from 26.1% to 30.79%, and porosity ranged from 81% to 83%. The change in water volume greatly affected the foam’s performance, the performance of foamed material deteriorated as the amount of added water increased, but the effect on thermal conductivity was not very obvious. The highest thermal conductivity was only 0.0179 W/(m·K), still providing excellent thermal insulation.

GEOLOLOGIC SITUATION IN THE AYDAR-ARNASAY COLONY AND ITS ATROPHY

The dynamic changes in water volume, the composition of the water and the geoecological situation around the lake system OF Aydar-Arnasayhave been studied from 1969 to 2018.

Patterns and causes of changes in water level and volume in Tangra Yumco from 1988 to 2018 based on Landsat images and Sentinel-3A synthetic aperture radar

湖泊变化是气候变化的指示器.为探索利用单一短时间尺度的卫星水位数据源估算长时间序列的湖泊水量变化的可行性，本文利用短时间尺度（2016—2018年）Sentinel-3A合成孔径雷达高度计（SRAL）作为唯一卫星水位数据源，以藏北高原内陆湖泊当惹雍错为例，结合基于Landsat光学遥感数据提取的1988—2018年的湖泊面积，综合分析2016—2018年间的非结冰期遥感湖泊面积与遥感湖泊水位变化，基于该时段范围的水位变化-面积变化关系和水量估算公式，估算1988—2018年湖泊水位水量变化与2001—2018年的年内变化，并结合GLDAS产品数据与雪线变化情况初步探讨湖泊变化的可能原因.结果表明：当惹雍错近30年湖泊面积扩张明显，湖泊水位、水量增加显著，相比1988年，2018年的湖泊面积、水位、水量分别增加21.1 km2、5.29 m、44.75亿m3.其中1988—1998年湖泊面积-水位-水量有所减少，2000—2018年间湖泊变化总体呈增加趋势.2001—2018年内湖泊面积、水位、水量变化呈现干湿季特征.1996—2014/2015年湖泊水量变化为38.3亿/35.5亿m3，水量变化趋势、变化量与以往对应时间段的研究结果具有较强的一致性.湖泊面积扩张主要发生在水下地形平缓的东南部和中西部区域.结合气候因素与雪线变化的分析表明，湖泊水量变化受降雨、气温影响复杂，长时间年际尺度上的湖泊水量增长与气温的一致性较降水量强，湖泊湿季受降水量与气温的影响都较大，其中2008—2018年的湿季降水量、气温与水量变化散点拟合的确定性系数R2分别为0.613、0.845.该研究表明Sentinel-3A合成孔径雷达数据在湖泊水量变化估算上的潜力，为利用单一且只具有短时段数据的卫星雷达数据估算长时间序列湖泊水量变化提供依据.

Investigation of Physiological Swelling on Conductivity Distribution in Lower Leg Subcutaneous Tissue by Electrical Impedance Tomography.

There is a strong need for a non-invasive measurement technique that is capable of accurately identifying the physiological condition change or heterogeneity of subcutaneous adipose tissue (SAT) by localizing the abnormalities within the compartment. This paper aims to investigate the feasibility of Electrical Impedance Tomography (EIT) to assess the interstitial fluid in subcutaneous adipose tissue as an enhancement method of bioelectrical impedance spectroscopy (BIS). Here, we demonstrate the preliminary result of EIT with a wearable 16 electrodes sensor. The image-based reference EIT with fat weighted threshold method is proposed. In order to evaluate the performance of our novel method, a physiological swelling experiment is conducted, and Multi-Frequency Bioelectrical Impedance Analysis (MFBIA) is also applied as a comparison with EIT results. The experimental results showed that the proposed method was able to distinguish the physiological swelling condition and effectively to remove the unexpected background noise. Furthermore, the conductivity variation in the subcutaneous layer had a good correlation with extracellular water volume change from MFBIA data; the correlation coefficient R2 = 0.927. It is concluded that the proposed method provides a significant prospect for SAT assessment.

Tracking Multidecadal Lake Water Dynamics with Landsat Imagery and Topography/Bathymetry

AbstractWater resource management is of critical importance due to its close relationship with nearly every industry, field, and lifeform on this planet. The success of future water management will rely upon having detailed data of current and historic water dynamics. This research leverages Google Earth Engine and uses Landsat 5 imagery in conjunction with bathymetry and Shuttle Radar Topography Mission digital elevation model data to analyze long‐term lake dynamics (water surface elevation, surface area, volume, volume change, and frequency) for Lake McConaughy in Nebraska, USA. Water surface elevation was estimated by extracting elevation values from underlying bathymetry and digital elevations models using 5,994 different combinations of water indices, water boundaries, and statistics for 100 time periods spanning 1985–2009. Surface elevation calculations were as accurate as 0.768 m root mean square error (CI95% [0.657, 0.885]). Water volume change calculations found a maximum change of 1.568 km3 and a minimum total volume of only 23.97% of the maximum reservoir volume. Seasonal and long‐term trends were identified, which have major affects regarding regional agriculture, local recreation, and lake water quality. This research fills an existing gap in optical remote sensing‐based monitoring of lakes and reservoirs, is more robust and outperforms other commonly used monitoring techniques, increases the number of water bodies available for long‐term studies, introduces a scalable framework deployable within Google Earth Engine, and enables data collection of both gauged and ungauged water bodies, which will substantially increase our knowledge and understanding of these critical ecosystems.

Salt Sinking in the Upper South Pacific Subtropical Gyre From 2004 to 2016

AbstractThe salinity in the 50–300‐m water column of the South Pacific subtropical gyre (10°S–30°S) increased from 2004 to 2016. The observed changes are primarily associated with changes in the South Pacific Tropical Water (SPTW) volume, which increased at a rate of (3.17 ± 0.25) 1014 m3 per decade in the region of 10–30°S and 150°E–90°W. The increases in the SPTW volume are caused by increased SPTW production, which increased at a rate of 3.45 ± 2.65 Sv per decade. The temporal variability in the mixed layer accounts for 75 ± 32% of the observed increase in SPTW production. The increases in temporal changes in the mixed layer are due to a deeper mixed layer depth (MLD) in austral winter and a shallower MLD in austral spring. The possible drivers of MLD changes at the air‐sea surface are examined. Among the wind stress curl, buoyancy fluxes, and the turbulence induced by wind stress, changes in the surface buoyancy fluxes play the most important role in the deepening of the MLD during austral winter, and changes in the wind stress play a leading role in the shoaling of the MLD during austral spring. Changes in the buoyancy fluxes during winter and changes in the wind stress in spring can be attributed to increases in the Southern Annular Mode from 2004 to 2016. This study highlights the strong modulation of SPTW formation by decadal climate variability over the subtropical South Pacific.

River Discharge Estimation based on Satellite Water Extent and Topography: An Application over the Amazon

Abstract River discharge (RD) estimates are necessary for many applications, including water management, flood risk, and water cycle studies. Satellite-derived long-term GIEMS-D3 surface water extent (SWE) maps and HydroSHEDS data, at 90-m resolution, are here used to estimate several hydrological quantities at a monthly time scale over a few selected locations within the Amazon basin. Two methods are first presented to derive the water level (WL): the “hypsometric curve” and the “histogram cutoff” approaches at an 18 km × 18 km resolution. The obtained WL values are interpolated over the whole water mask using a bilinear interpolation. The two methods give similar results and validation with altimetry is satisfactory, with a correlation ranging from 0.72 to 0.89 in the seven considered stations over three rivers (i.e., Wingu, Negro, and Solimoes Rivers). River width (RW) and water volume change (WVC) are also estimated. WVC is evaluated with GRACE total water storage change, and correlations range from 0.77 to 0.88. A neural network (NN) statistical model is then used to estimate the RD based on four predictors (SWE, WL, WVC, and RW) and on in situ RD measurements. Results compare well to in situ measurements with a correlation of about 0.97 for the raw data (and 0.84 for the anomalies). The presented methodologies show the potential of historical satellite data (the combination of SWE with topography) to help estimate RD. Our study focuses here on a large river in the Amazon basin at a monthly scale; additional analyses would be required for other rivers, including smaller ones, in different environments, and at higher temporal scale.

On the Field Estimation of Moisture Content Using Electrical Geophysics: The Impact of Petrophysical Model Uncertainty

AbstractThe spatiotemporal distribution of pore water in the vadose zone can have a critical control on many processes in the near‐surface Earth, such as the onset of landslides, crop yield, groundwater recharge, and runoff generation. Electrical geophysics has been widely used to monitor the moisture content (θ) distribution in the vadose zone at field sites, and often resistivity (ρ) or conductivity (σ) is converted to moisture contents through petrophysical relationships (e.g., Archie's law). Though both the petrophysical relationships (i.e., choices of appropriate model and parameterization) and the derived moisture content are known to be subject to uncertainty, they are commonly treated as exact and error‐free. This study examines the impact of uncertain petrophysical relationships on the moisture content estimates derived from electrical geophysics. We show from a collection of data from multiple core samples that significant variability in the θ(ρ) relationship can exist. Using rules of error propagation, we demonstrate the combined effect of inversion and uncertain petrophysical parameterization on moisture content estimates and derive their uncertainty bounds. Through investigation of a water injection experiment, we observe that the petrophysical uncertainty yields a large range of estimated total moisture volume within the water plume. The estimates of changes in water volume, however, generally agree within (large) uncertainty bounds. Our results caution against solely relying on electrical geophysics to estimate moisture content in the field. The uncertainty propagation approach is transferrable to other field studies of moisture content estimation.

Muscle Glycogen Content during Endurance Training under Low Energy Availability

The present study investigated the effects of three consecutive days of endurance training under conditions of low energy availability (LEA) on the muscle glycogen content, muscle damage markers, endocrine regulation, and endurance capacity in male runners. Seven male long-distance runners (19.9 ± 1.1 yr, 175.6 ± 4.7 cm, 61.4 ± 5.3 kg, maximal oxygen uptake [V˙O2max]: 67.5 ± 4.3 mL·kg·min) completed two trials consisting of three consecutive days of endurance training under LEA (18.9 ± 1.9 kcal·kg FFM·d) or normal energy availability (NEA) (52.9 ± 5.0 kcal·kg FFM·d). The order of the two trials was randomized, with a 2-wk interval between trials. The endurance training consisted of 75 min of treadmill running at 70% of V˙O2max. Muscle glycogen content, respiratory gas variables, and blood and urine variables were measured in the morning for three consecutive days of training (days 1-3) and on the following morning after training (day 4). As an indication of endurance capacity, time to exhaustion at 19.0 ± 0.8 km·h to elicit 90% of V˙O2max was evaluated on day 4. During the training period, body weight, fat-free mass, and skeletal muscle volume were significantly reduced in LEA (P = 0.02 for body weight and skeletal muscle volume, P = 0.01 for fat-free mass). Additionally, muscle glycogen content was significantly reduced in LEA (~30%, P < 0.001), with significantly lower values than those in NEA (P < 0.001). Time to exhaustion was not significantly different between the two trials (~20 min, P = 0.39). Three consecutive days of endurance training under LEA decreased muscle glycogen content with lowered body weight. However, endurance capacity was not significantly impaired.

Monitoring Groundwater Storage Depletion Using Gravity Recovery and Climate Experiment (GRACE) Data in Bakhtegan Catchment, Iran

The Bakhtegan catchment, an important agricultural region in south-western Iran, has suffered groundwater depletion in recent years. As groundwater is considered the main source of fresh water in the catchment, especially for agriculture, monitoring groundwater responses to irrigation is important. Gravity Recovery and Climate Experiment (GRACE) satellite data can help determine water mass changes in catchments and assess water volume changes. In this study, we compared GRACE-derived water mass data against groundwater volume variations measured in situ. We also assessed the efficiency of GRACE-derived data in catchments smaller than the 200,000 km2 recommended area when using GRACE. For the study period (January 2002 through December 2011), the GRACE data showed a 7.6 mm annual decline in groundwater level, with a total volume loss of 2.6 km3 during the period. The in situ monthly measurements of groundwater level showed an average depletion of 10 m in catchment aquifers during the study period. This depletion rate was supported by the recorded decrease in precipitation volume, especially in the post-drought period after 2007. These results demonstrate that GRACE can be useful tool for monitoring groundwater depletion in arid catchments.