Atmospheric Isotopologues of water vapor (e.g., HDO) are important tracers for understanding earth’s hydrological cycle. Concentration variations of water isotopologues are driven by phase changes in a process referred to as fractionation. During fractionation process, heavier isotopologues (i.e., HDO) are more likely to condense and less likely to evaporate. As a result, fractionation of HDO allows measurements of water isotopologue concentrations to serve as a proxy for observing water vapor movement through the global hydrological cycle. In this study, we examine the total column retrievals of H2O and HDO from the Total Carbon Column Observing Network (TCCON) observations to understand the spatial and temporal characteristics of atmospheric HDO. TCCON is a ground-based network of Fourier Transform Spectrometers that observe direct solar spectra in the near infrared spectral region in order to accurately and precisely retrieve column-averaged abundances of H2O and HDO. H2O column reported in the TCCON data product is the mean of retrievals from fifteen spectral windows and for XHDO it is from six spectral windows in the near infrared spectral region. There are currently 24 operational TCCON sites that are located globally and most of them has more than 5 years’ measurements. Using these TCCON H2O and HDO retrievals, we investigate the seasonal and inter-annual variabilities of atmospheric water vapor and its stable isotope of HDO. We further explore the usages of HDO/H2O ratio to trace the origin of atmospheric water vapor.  

With the rise of research on new artificial rainfall technologies in recent years, the idea of guiding the redistribution of cloud water resources using acoustic waves has gradually come to fruition. In addition to simulating and analyzing the effect of the acoustic wave on movement of particle aerosols from a microscopic point of view in laboratory experiments, it is also necessary to investigate the attenuation features of acoustic waves in the actual atmosphere. However, due to objective conditions and technical limitations, the current researches on atmosphere acoustic attenuation are limited. In this study, an outdoor atmospheric acoustic attenuation experiment in Tibet was conducted and sound pressure level (SPL) data at different positions within a height of 500 m are obtained. Then, using COMSOL Multiphysics, this study verified the experimental results, and further obtained the basic features and influencing factors of atmospheric acoustic attenuation. In the study, the actual effective impact area of atmospheric acoustic attenuation at different altitudes are quantified. On this basis, we further set up different analog models by adjusting the placement and numbers of acoustic source to find an optimal solution to control acoustic wave attenuation. The study results will be invaluable to further conduct evaluation of efficiency of acoustic-stimulated precipitation as a whole.

Acoustic induced precipitation has drawn widely attentions from researchers in recent years. However, the mechanism of this technology is complex and still unclear. Particle size is a significant factor of the acoustic induced agglomeration process. Water droplets in the cloud have a broad particle size distribution. Until now, there only have several experimental studies on the particle motion in the sound field and have proved the theoretical formula of large particle movement induced by sound wave. In this study, the particle image velocimetry system was employed to detect the particle motion in travelling wave fields with low frequencies and high sound pressure levels. The experimental results were compared with the results from the theoretical analysis. Then, it can be concluded that for most of the ranges of acoustic frequencies the fine particle vibration amplitudes have a rational agreement with the analytical results. Nevertheless, there are two ranges of acoustic frequencies, the velocity amplitudes of the experimental results are considerably smaller than the analytical ones. Since there is a multiple relationship between both the ranges, it is induced that those acoustic frequencies reflect the experimental equipment frequency. In other words, the equipment resonance frequency can significantly influence the fine particle movement and reduce the velocity amplitude by up to 40%.

Soil water content (SWC) is a vital factor for soil sciences. Nowadays, there are many methods for estimating SWC, including the Time-domain reflectometry (TDR) and the Gravimetric method. Nevertheless, most of them may cause damages to soil structure and require a large workforce and resources. The optical method is a non-destructive and cost-efficient; therefore, recommended for SWC estimations. This study analyses soil samples at the field site, as well as it uses aerial photo-shooting to obtain the digital image distribution of surface soil. Both soil samples and digital images were categorized into groups; 9 in total, depending on time parameters (one group equals one day). More specifically, the gravimetric method was selected for the SWC measurements in the laboratory, while the images were modified in such a way so to match the Near Infrared Spectroscopy (NIR) resolution for further calculations. Then, comparing the NIR data with the Soil Water Content correlation of 9 groups by validation. According to the findings, the sensitivity of NIR in SWC alternations is high. Additionally, it can be observed that the SWC result data of the model are similar to the SWC measurements; therefore, the NIR can be applied to agriculture and disaster prevention, and it is a cost-efficient method for SWC estimations, and it can provide several benefits.

The traditional method of analyzing soil salinity is to measure electrical conductivity (EC). The methods of measuring EC are in-situ measurement and laboratory test. Both methods require plenty resources besides the high cost. For the in-situ, remote sensing techniques for identifying soil salinity can be detect by either satellite or airborne remote sensing. The disadvantage of satellite remote sensing is unable to obtain a continuous image data and the image resolution is low. In recent years, most of the unmanned aerial vehicle (UAV) remote has install camera, such as: digital, multispectral, thermal, or hyperspectral. Due to its the high image resolution and shooting frequency, it has successfully to investigate the distribution of soil salinity. In past studies have not investigate the relationship between EC and Near-Infrared (NIR) reflectance under the different particle sizes of a soil type. Furthermore, most of the UAVs’ cameras are digital or hyperspectral cameras, not the NIR camera.In the laboratory, using NIR camera to investigate the correlation between the EC and NIR reflectance of standard quartz sand in a darkroom. For the in-situ, use a UAV with NIR camera to shooting the salinity soil in a specific area, collects NIR image to obtain the red light (R) and NIR reflectance. Then, Calculate the Normalized Difference Vegetation Index (NDVI) by the R and NIR reflectance and found out the relationship between the EC and NDVI. According to the findings, the correlation of EC and NIR reflectance of standard quartz sand is high. Additionally, it can be observed that the NDVI distribution are similar with EC distribution in a specific area. therefore, the UAV with NIR camera can be applied to agriculture and disaster prevention, and it is a cost-efficient method for soil salinity estimations.

Afghanistan economy is highly depending on the agriculture and livestock while farmers suffer from water shortage and drought. The Balkhab River basin (BRB) in the northern Afghanistan was selected as study area. The Soil and Water Assessment Tools (ArcSWAT) has been used for the watershed modeling. Climate data for precipitation, temperature, and relative humidity on a daily basis are used from five hydrometeorological stations in BRB. In addition, the daily wind speed and solar radiation dataset were retrieved from NASA Prediction of Worldwide Energy Resources. The UNFAO global soil map has been obtained for the entire study area. Land use and land cover map for Afghanistan was also retrieved from UNFAO for the year 2010. The Digital Elevation Model from ALOS PLASAR with a resolution of 12.5 m was retrieved and utilized. The SWAT model was developed using mentioned dataset for the period of 2010 to 2018. The study period divided into warmup (2010 to 2012), calibration (2013 to 2015), and validation (2016 to September 2018). Monthly average observed discharges in the four stations; Rabat-i-Bala, Pul-i-Baraq, Doshqadam, and Nazdik-i-Nayak from downstream to upstream were used for the model verification, and coefficient of determination (R²) and Nash-Sutcliff model efficiency coefficient (NSE) were used for the performance assessment. In the calibration/validation periods, the R² values were 0.70/0.63, 0.86/0.66, 0.67/0.58, and 0.80/0.76 respectively in the Rabat-i-Bala, Pul-i-Baraq, Doshqadam, and Nazdik-i-Nayak; and the NSEs were 0.52/0.58, 0.83/0.61, 0.40/0.47 and 0.57/0.43. Then, the water allocation of irrigation canals was reformed considering crop water requirement and a dam was proposed into SWAT model in BRB downstream for agricultural water resource allocation. While currently farmers are facing water difficulty, the investigations showed that the BRB has a good capacity for irrigation of existing lands as well as extra 88,706 ha lands with the proposed dam construction.

Groundwater flow system in urban areas is more complex than that in non-urban areas due to the integration of anthropogenic and hydrogeological factors. The tracer approach using stable isotopes are valuable tools to identify the source of groundwater, which is essential for water management in urban areas. This study focused on the groundwater flow system in the Klang River basin where Kuala Lumpur is located. The Klang river basin is underlain by complex structures such as granite, limestone, and sedimentary rock. We conducted sampling campaigns for river water, groundwater, and rainwater in September 2019 and January through March 2020. Oxygen and hydrogen stable isotopes and dissolved ion concentrations were determined on all water samples. These chemical compositions were used as tracers to investigate the groundwater flow system. Stable isotope values of river water and groundwater are plotted along the local meteoric water line on the delta-diagram, and there are no significant signals of evaporation throughout the recharge process in the isotopic composition. The oxygen-18 values in the main river water decrease as the elevation increases in the upstream area, whereas the oxygen-18 of groundwater decreases as the elevation of the well's screen decreases. Also, the oxygen-18 of groundwater in the lowland areas is lower than that of river water sampled at an elevation higher than 70 m, indicating that the groundwater in the lowland area is recharged dominantly above the elevation of 70 m, where is covered by forests. Additionally, the principal component analysis and cluster analysis by using chemical compositions show that the groundwater samples are classified into two groups, which shows that the groundwater in the downstream area is recharged mainly at mountainous and hilly areas. We believe our study serves new findings on the groundwater flow system in mega-cities of the tropical climate regions.

The degradation of Groundwater (GW) has caused many health-related severe problems to the human and animals due to the exposure of a variety of toxic and hazardous contaminants. Development of effective and sustainable remediation technology is the need of the hour, especially in developing countries like India. Among the various GW remediation techniques adopted worldwide, Permeable Reactive Barrier is considered as one of the most effective and well established in-situ remediation method. Three different PRB design configurations, i.e., continuous PRB, funnel-and-gate PRB and drain-and-gate, are used for the filed application of PRB worldwide. The remediation efficiency of these three design configurations shows variation. Therefore, evaluation of the long-term performance of PRB of different design configurations is essential prior to their field-scale emplacement to avoid any potential failure in future. In this study, numerical modelling of the three design configurations of PRB using MODFLOW (flow model) and MT3DMS (solute-transport model) is performed on the Bhalswa landfill site in Delhi, India. The target contaminant for removal is Hexavalent Chromium. Iron powder is selected as the reactive material. Batch experiments are conducted to find the isotherm and kinetic parameters needed for developing the PRB model. The results show that the contaminated plume (coming from the landfill site) is effectively contained by PRB. Among the three PRB design configurations, drain-and-gate PRB performs the best, followed by funnel-and-gate PRB and continuous PRB. This study will aid in field emplacement of PRB by identifying the best-suited design configurations over the concerning site.

Since the successful launch of the Gravity Recovery and Climate Experiment (GRACE) on March 17^th, 2002, a number of scientists have adopted satellite gravimetry for the detection of variations on terrestrial water storage (TWS). Use of high-precision GRACE gravimetry presents advantages in hydrogeologic studies, such as providing accurate estimates of currents and gravity fields. Many studies have proven that the high-precision GRACE gravimetry can observe large-scale (over 50,000 km²) variations in groundwater storage (GWS). However, relatively few studies conducted using satellite gravimetry have focused on scales smaller than 5,000 km². The purpose of this study is to investigate the potential for using GRACE gravimetry to observe small-scale variations in GWS specifically, this paper presents a case study of the Zhoushui River alluvial fan (~2,560 km²) in central Taiwan as an example of how well GRACE data compare to field-based data for ascertaining small-scale variations in GWS. Field measurements of groundwater level in 66 observation wells (April 2002 to June 2020) were used to analyze variations in GWS. Results of this field-based analysis were compared to results obtained using the GWS data (April 2002 to June 2020) obtained by GRACE gravimetry. This comparison allowed us to evaluate the similarities and differences in both methods as well as to prove the feasibility of using GRACE gravimetry in small-scale regions. Results of our comparative analysis indicate that water resources in small watershed can be successfully managed using gravimetric data collected by GRACE satellite.

Terrestrial water storage is a vital component of the hydrologic cycle for a holistic understanding of the prevailing earth system processes in any region. GRACE satellites have recorded the real-time variations in TWS over the past two decades, including both natural and anthropogenic factors. In this study, two mascon-based gravity anomaly products from CSR and JPL were utilized to get equivalent water thickness anomalies (and corresponding volume) of terrestrial water storage (TWS) from May 2002 to April 2017 over Japan. Co-seismic and post-seismic effects that occurred due to the Tohoku‐Oki earthquake (March 11, 2011; M_w 9.0) were removed by the least square fitting of the TWS time series at each grid location in the study region. The e-folding relaxation time was taken as four months. The corrected time series showed a linearly decreasing trend of -2.24 mm yr^-1 (equivalent to -0.81 km³ yr^-1) compared to the raw TWS anomaly trends of -7.87 mm yr^-1 (-2.85 km³ yr^-1). Further analysis of water storage deficits revealed two significant TWS deficits from 2007-2009 and 2011-2016, with groundwater as the primary contributor to TWS. These results of declining TWS highlight the need to revisit the existing water management strategies for sustainable water usage.

The increase in impermeability due to urbanization leads to increased surface runoff, reduced infiltration, and reduced evaporation, resulting in unbalanced natural water circulation. The concentrated population density leads to an increase in water consumption, which generates an increase in regional water supply dependence, exacerbating the artificial water cycle distortion. This study aims to establish a balanced urban water cycle, and present a blueprint of it. The balanced urban water cycle was defined in terms of sustainability, safety, equity, and efficiency according to the water cycle-related literature particularly OECD (Organisation for Economic Co-operation and Development), and UN-Water (United Nations Water). In this study, sustainability, equity, safety, and efficiency were defined as the securing of water circulation management system adapted to future climate change, the absence of inequity in the movement of water spatially, less damage to property and life caused by water, and the securing of the right amount of clear water to anyone, respectively. To propose the appropriate state of the urban water cycle, evaporation rate, runoff rate (surface water, subsurface water, groundwater), soil moisture rate, and groundwater content rate were selected as indicators. The details on the four aspects (sustainability, equity, safety, and efficiency) presented in the definition are analyzed with major cities in Korea concerning yearly statistical data. By comparing the state with the four aspects to the state following the six indicators described above, the most legitimate state was suggested. As a result, we propose a well-suited urban water circulation, which will lead to the restoration of the balanced urban water cycle and sustainable urban development.