Investigation of the climate change effects on drought is required to develop management strategies for minimizing adverse social and economic impacts. Therefore, studying the future meteorological drought conditions at a local scale is vital. In this study, we assessed the efficiency of seven downscaled Global Climate Models (GCMs) provided by the NASA Earth Exchange Global Daily Downscaled Projections (NEX-GDDP), and investigated the impacts of climate change on future meteorological drought using Standard Precipitation Index (SPI) in the Karoun River Basin (KRB) of southwestern Iran under two Representative Concentration Pathway (RCP) emission scenarios, i.e., RCP4.5 and RCP8.5. The results demonstrated that SPI estimated based on the Meteorological Research Institute Coupled Global Climate Model version 3 (MRI-CGCM3) is consistent with the one estimated by synoptic stations during the historical period (1990-2005). The root mean square error (RMSE) value is less than 0.75 in 77% of the synoptic stations. GCMs have high uncertainty in most synoptic stations except those located in the plain. Using the average of a few GCMs to improve performance and reduce uncertainty is suggested by the results. The results revealed that with the areas affected by wetness decreasing in the KRB, drought frequency in the North KRB is likely to increase at the end of the 21^st century under RCP4.5 and RCP8.5 scenarios. At the seasonal scale, the decreasing trend for SPI in spring, summer, and winter shows a drought tendency in this region. The climate-induced drought hazard can have vast consequences, especially in agriculture and rural livelihoods. Accordingly, an increasing trend in drought during the growing seasons under RCP scenarios is vital for water managers and farmers to adopt strategies to reduce the damages. The results of this study are of great value for formulating sustainable water resources management plans affected by climate change.

The Dunhuang-Golmud railway passes through different deserts in arid areas, especially drifting-sand desert and sandy-gravel Gobi. The near-surface wind environment and wind-sand transport process vary due to different external factors, such as topography, vegetation, and regional climate, resulting in evident spatial differences in surface erosion and deposition. Consequently, the measures for preventing wind-sand hazards will differ. However, the mechanism and control theory of sand damage remain poorly understood. In this study, we used meteorological observation, three-dimensional (3D) laser scanning, and grain-size analysis to compare and evaluate the spatial distribution of wind conditions, sand erosion and deposition patterns, and grain composition in the drifting-sand desert and sandy-gravel Gobi along the Dunhuang-Golmud railway in China. Results show that the annual mean wind speed, the frequency of sand-driving wind, and the drift potential of sandy-gravel Gobi are higher than those of drifting-sand desert, indicating a greater wind strength in the sandy-gravel Gobi, which exhibits spatial heterogeneity in wind conditions. The major sediment components in sandy-gravel Gobi are very fine sand, fine sand, and medium sand, and that in drifting-sand desert are very fine sand and fine sand. We found that the sediment in the sandy-gravel Gobi is coarser than that in the drifting-sand desert based on mean grain size and sediment component. The spatial distributions of sand erosion and deposition in the sandy-gravel Gobi and drifting-sand desert are consistent, with sand deposition mainly on the west side of the railway and sand erosion on the east side of the railway. The area of sand deposition in the drifting-sand desert accounts for 75.83% of the total area, with a mean deposition thickness of 0.032 m; while the area of sand deposition in the sandy-gravel Gobi accounts for 65.31% of the total area, with a mean deposition thickness of 0.028 m, indicating greater deposition amounts in the drifting-sand desert due to the presence of more fine sediment components. However, the sand deposition is more concentrated with a greater thickness on the embankment and track in the sandy-gravel Gobi and is dispersed with a uniform thickness in the drifting-sand desert. The sand deposition on the track of the sandy-gravel Gobi mainly comes from the east side of the railway. The results of this study are helpful in developing the preventive measures and determining appropriate selection and layout measures for sand control.

In Tunisia, water scarcity is only adding pressure on water demand in agriculture. In the context of sustainable development goals, Tunisia has been reusing treated wastewater (TWW) as a renewable and inexpensive source for soil fertigation and groundwater (GW) recharge. However, major risks can be expected when the irrigation water is of poor quality. This study aims for evaluating the potential risk of TWW and GW irrigation on soil parameters. Accordingly, we evaluated the suitability of water quality through the analysis of major and minor cations and anions, metallic trace elements (MTEs), and the sodium hazard by using the sodium adsorption ratio (SAR) and the soluble sodium percentage (SSP). The risk of soil sodicity was further assessed by SAR and the exchangeable sodium percentage (ESP). The degree of soil pollution caused by MTEs accumulation was evaluated using geoaccumulation index (Igeo) and pollution load index (PLI). Soil maps were generated using inverse spline interpolation in ArcGIS software. The results show that both water samples (i.e., TWW and GW) are suitable for soil irrigation in terms of salinity (electrical conductivity<7000 μS/cm) and sodicity (SAR<10.00; SSP<60.00%). However, the contents of PO₄^3-, Cu²⁺, and Cd²⁺ exceed the maximum threshold values set by the national and other standards. Concerning the soil samples, the average levels of SAR and ESP are within the standards (SAR<13.00; ESP<15.00%). On the other hand, PLI results reveal moderate pollution in the plot irrigated with TWW and no to moderate pollution in the plot irrigated with GW. Igeo results indicate that Cu²⁺ is the metallic trace element (MTE) with the highest risk of soil pollution in both plots (Igeo>5.00), followed by Ni²⁺ and Pb²⁺. Nevertheless, Cd²⁺ presents the lowest risk of soil pollution (Igeo<0.00). Statistical data indicates that Ca²⁺, Na⁺, Ni²⁺, and Pb²⁺ are highly distributed in both plots (coefficient of variation>50.0%). This study shows that the use of imagery tools, such as ArcGIS, can provide important information for evaluating the current status of soil fertility or pollution and for better managing soil irrigation with TWW.

In the current scenario, Lake Urmia, one of the vastest hyper saline lakes on the Earth, has been affected by serious environmental degradation. Using different satellite images and observational data, this study investigated the changes in the lake for the period 1970-2020 based on the effects of climate change and several human-induced processes on Lake Urmia, such as population growth, excessive dam construction, low irrigation water use efficiency, poor water resources management, increased sediment flow into the lake, and lack of political and legal frameworks. The results indicated that between 1970 and 1997, the process of change in Lake Urmia was slow; however; the shrinkage was faster between 1998 and 2018, with about 30.00% of the lake area disappearing. As per the findings, anthropogenic factors had a much greater impact on Lake Urmia than climate change and prolonged drought; the mismanagement of water consumption in the agricultural sector and surface and underground water withdrawals in the basin have resulted in a sharp decrease in the lake's surface. These challenges have serious implications for water resources management in Lake Urmia Basin. Therefore, we provided a comprehensive overview of anthropogenic factors on the changes in Lake Urmia along with existing opportunities for better water resources management in Lake Urmia Basin. This study serves as a guideline framework for climate scientists and hydrologists in order to assess the effects of different factors on lake water resources and for decision-makers to formulate strategies and plans according to the management task.

The preceding and succeeding precipitation (PSP) often act together with extreme precipitation (EP), in turn, causing floods, which is an objective component that is often overlooked with regard to summer flood hazards in the arid region of Northwest China. In this study, event-based extreme precipitation (EEP) was defined as continuous precipitation that includes at least one day of EP. We analyzed the spatiotemporal variation characteristics of four EEP types (front EEP, late EEP, balanced EEP, and single day EEP) across the Loess Plateau (LP) based on data acquired from 87 meteorological stations from 1960 to 2019. Precipitation on the LP basically maintained a spatial pattern of "low in the northwest region and high in the southeast region", and EP over the last 10 a increased significantly. The cumulative precipitation percentage of single day EEP was 34% and was dominant for 60 a, while the cumulative precipitation percentage of front, late, and balanced EEP types associated with PSP accounted for 66%, which confirms to the connotation of EEP. The cumulative frequencies of front and late EEP types were 23% and 21%, respectively, while the cumulative frequency of balanced EEP had the lowest value at only 13%. Moreover, global warming could lead to more single day EEP across the LP, and continuous EEP could increase in the northwestern region and decrease in the eastern region in the future. The concept of process-oriented EP could facilitate further exploration of disaster-causing processes associated with different types of EP, and provide a theoretical basis for deriving precipitation disaster chains and construction of disaster cluster characteristics.

North Africa is one of the most regions impacted by water shortage. The implementation of controlled drainage (CD) in the northern Nile River delta of Egypt is one strategy to decrease irrigation, thus alleviating the negative impact of water shortage. This study investigated the impacts of CD at different levels on drainage outflow, water table level, nitrate loss, grain yield, and water use efficiency (WUE) of various wheat cultivars. Two levels of CD, i.e., 0.4 m below the soil surface (CD-0.4) and 0.8 m below the soil surface (CD-0.8), were compared with subsurface free drainage (SFD) at 1.2 m below the soil surface (SFD-1.2). Under each drainage treatment, four wheat cultivars were grown for two growing seasons (November 2018-April 2019 and November 2019-April 2020). Compared with SFD-1.2, CD-0.4 and CD-0.8 decreased irrigation water by 42.0% and 19.9%, drainage outflow by 40.3% and 27.3%, and nitrate loss by 35.3% and 20.8%, respectively. Under CD treatments, plants absorbed a significant portion of their evapotranspiration from shallow groundwater (22.0% and 8.0% for CD-0.4 and CD-0.8, respectively). All wheat cultivars positively responded to CD treatments, and the highest grain yield and straw yield were obtained under CD-0.4 treatment. Using the initial soil salinity as a reference, the soil salinity under CD-0.4 treatment increased two-fold by the end of the second growing season without negative impacts on wheat yield. Modifying the drainage system by raising the outlet elevation and considering shallow groundwater contribution to crop evapotranspiration promoted water-saving and WUE. Different responses could be obtained based on the different plant tolerance to salinity and water stress, crop characteristics, and growth stage. Site-specific soil salinity management practices will be required to avoid soil salinization due to the adoption of long-term shallow groundwater in Egypt and other similar agroecosystems.

Drought, which restricts the sustainable development of agriculture, ecological health, and social economy, is affected by a variety of factors. It is widely accepted that a single variable cannot fully reflect the characteristics of drought events. Studying precipitation, reference evapotranspiration (ET₀), and vegetation yield can derive information to help conserve water resources in grassland ecosystems in arid and semi-arid regions. In this study, the interactions of precipitation, ET₀, and vegetation yield in Darhan Muminggan Joint Banner (DMJB), a desert steppe in Inner Mongolia Autonomous Region, China were explored using two-dimensional (2D) and three-dimensional (3D) joint distribution models. Three types of Copula functions were applied to quantitatively analyze the joint distribution probability of different combinations of precipitation, ET₀, and vegetation yield. For the precipitation-ET₀ dry-wet type, the 2D joint distribution probability with precipitation≤245.69 mm/a or ET₀≥959.20 mm/a in DMJB was approximately 0.60, while the joint distribution probability with precipitation≤245.69 mm/a and ET₀≥959.20 mm/a was approximately 0.20. Correspondingly, the joint return period that at least one of the two events (precipitation was dry or ET₀ was wet) occurred was 2 a, and the co-occurrence return period that both events (precipitation was dry and ET₀ was wet) occurred was 5 a. Under this condition, the interval between dry and wet events would be short, the water supply and demand were unbalanced, and the water demand of vegetation would not be met. In addition, when precipitation remained stable and ET₀ increased, the 3D joint distribution probability that vegetation yield would decrease due to water shortage in the precipitation-ET₀ dry-wet years could reach up to 0.60-0.70. In future work, irrigation activities and water allocation criteria need to be implemented to increase vegetation yield and the safety of water resources in the desert steppe of Inner Mongolia.