Irrigation In Arid Areas Research Articles

Limited irrigation and fertilization in sand-layered soil increases nitrogen use efficiency and economic benefits under film mulched ridge-furrow irrigation in arid areas

Hetao Irrigation District (HID) in the upper Yellow River Basin of China is vulnerable due to the scarcity of water resources and environmental pollution caused by nutrient leaching. Appropriate irrigation and fertilization management are essential for improving crop productivity and developing sustainable agriculture in the HID. A two-year field experiment investigated the effects of irrigation and fertilization regimes on soil water, nitrogen accumulation and distribution in the soil profile and plant organs, nitrogen use efficiency, and economic benefits of spring maize (Zea mays L.) under film mulched ridge–furrow system. Three irrigation levels—I1 (high, 400 mm), I2 (medium, 300 mm), and I3 (low, 200 mm)—and two fertilization levels—F1 (high, 300 kg N ha−1) and F2 (low, 150 kg N ha−1) were designed. Mean soil NO3−-N contents did not significantly differ between I2 and I3 and were significantly higher than I1. I1F1 and I1F2 remarkably increased soil NO3−-N accumulation in the 80 − 100 cm soil layer at harvest. High irrigation increased the risk of N leaching into the deep soil layer. I2F2 increased plant nitrogen accumulation and promoted nitrogen transport to grains, improved nitrogen harvest index, and internal use efficiency. Under 400 or 300 mm irrigation amount, soil moisture and plant growth had little difference. Grain yields among I1F1, I1F2, I2F1, and I2F2 did not significantly differ in 2017 and 2018. In the relatively poor rainfall year (2017), I2F2 had 13.1%, 211.8%, and 294.1% higher net income than I2F1, I3F1, and I3F2, respectively, but 24.5% and 33.0% lower net income than I1F1 and I1F2, respectively. In 2018 with normal rainfall, I2F2 had 38.5%, 4.8%, 29.5%, 114.3%, and 96.2% higher net income than I1F1, I1F2, I2F1, I3F1, and I3F2, respectively. Therefore, the film mulched ridge–furrow irrigation system with 300 mm irrigation and 150 kg N ha−1 fertilization is a promising approach for reducing water supply and nitrogen leaching, and obtaining acceptable grain yield and economic benefits for spring maize production in the upper Yellow River Basin of China.

Effect of salinity on oleic sunflower (Helianthus annuus Linn.) under drip irrigation in arid area of Northwest China

To achieve secure and efficient saline water irrigation in arid areas, a field experiment was conducted to evaluate the salt distribution in the soil profile and response of sunflower (Helianthus annuus L.) to salinity from 2018 to 2020. The experiment included five levels of irrigation water salinity (ECi = 0.5 dS/m, 3.3 dS/m, 4.9 dS/m, 6.6 dS/m and 8.2 dS/m). The results indicated that the soil salinity rose slightly and was maintained in balance in the first two years owing to the moderate freshwater irrigation after planting. In 2020, surface salinity accumulation occurred when the ECi was greater than 3.3 dS/m. The average soil salinity at 0–100 cm soil depth was near that of the irrigation water. The effects of irrigation water salinity on plant growth and yield were also investigated. Salinity hindered the growth of the sunflower, which was indicated by a decrease of plant height, biomass, and plant water content. Salinity also reduced sunflower yield by reducing the disk diameter and 100-grain weight. IWP increased in the first two years and then decreased in the third year with an increase in the irrigation water salinity. The salinity threshold for oleic sunflower was 1.3 dS/m, and the sunflower seed yield decreased by 4.9% for every 1 dS/m increase in soil salinity. To ensure a seed yield of over 75%, the soil salinity should be less than 6.4 dS/m. It was concluded that for oleic sunflower drip irrigation in arid areas, the plant, should be irrigated with 80 mm of freshwater to leach salt after planting. This not only ensures that the seed yield is no less than 85% but also maintains a balanced soil salinity after harvest when the ECi increases to 8.2 dS/m.

Deep Learning-Based Predictive Framework for Groundwater Level Forecast in Arid Irrigated Areas

An accurate groundwater level (GWL) forecast at multi timescales is vital for agricultural management and water resource scheduling in arid irrigated areas such as the Hexi Corridor, China. However, the forecast of GWL in these areas remains a challenging task owing to the deficient hydrogeological data and the highly nonlinear, non-stationary and complex groundwater system. The development of reliable groundwater level simulation models is necessary and profound. In this study, a novel ensemble deep learning GWL predictive framework integrating data pro-processing, feature selection, deep learning and uncertainty analysis was constructed. Under this framework, a hybrid model equipped with currently the most effective algorithms, including the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) for data decomposition, the genetic algorithm (GA) for feature selection, the deep belief network (DBN) model, and the quantile regression (QR) for uncertainty evaluation, denoted as CEEMDAN-GA-DBN, was proposed for the 1-, 2-, and 3-month ahead GWL forecast at three GWL observation wells in the Jiuquan basin, northwest China. The capability of the CEEMDAN-GA-DBN model was compared with the hybrid CEEMDAN-DBN and the standalone DBN model in terms of the performance metrics including R, MAE, RMSE, NSE, RSR, AIC and the Legates and McCabe’s Index as well as the uncertainty criterion including MPI and PICP. The results demonstrated the higher degree of accuracy and better performance of the objective CEEMDAN-GA-DBN model than the CEEMDAN-DBN and DBN models at all lead times and all the wells. Overall, the CEEMDAN-GA-DBN reduced the RMSE of the CEEMDAN-DBN and DBN models in the testing period by about 9.16 and 17.63%, while it improved their NSE by about 6.38 and 15.32%, respectively. The uncertainty analysis results also affirmed the slightly better reliability of the CEEMDAN-GA-DBN method than the CEEMDAN-DBN and DBN models at the 1-, 2- and 3-month forecast horizons. The derived results proved the ability of the proposed ensemble deep learning model in multi time steps ahead of GWL forecasting, and thus, can be used as an effective tool for GWL forecasting in arid irrigated areas.

Micro-Clustering and Rank-Learning Profiling of a Small Water-Quality Multi-Index Dataset to Improve a Recycling Process

The efficiency improvement of wastewater recycling has been prioritized by ‘Goal 6’ of the United Nations Sustainable Development initiative. A methodology is developed to synchronously profile multiple water-quality indices of a wastewater electrodialysis (ED) process. The non-linear multifactorial screener is exclusively synthesized by assembling proper R-based statistical freeware routines. In sync with current trends, the new methodology promotes convenient, open and rapid implementation. The new proposal unites the ‘small-and-fast’ data-sampling features of the fractional multifactorial designs to the downsizing, by microclustering, of the multiple water quality indices—using optimized silhouette-based classification. The non-linear multifactorial profiling process is catalyzed by the ‘ordinalization’ of the regular nominal nature of the resulting optimum clusters. A bump chart screening virtually eliminates weak performances. A follow-up application of the ordinal regression succeeds in assigning statistical significance to the resultant factorial potency. The rank-learning aptitude of the new profiler is tested and confirmed on recently published wastewater ED-datasets. The small ED-datasets attest to the usefulness to convert limited data in real world applications, wherever there is a necessity to improve the quality status of water for agricultural irrigation in arid areas. The predictions have been compared with other techniques and found to be agreeable.

Improving wheat grain yield via promotion of water and nitrogen utilization in arid areas

Crop yield is limited by water and nitrogen (N) availability. However, in Hexi Corridor of northwestern China, water scarcity and excessive fertilizer N in wheat (Triticum aestivum L.) production causes serious conflicts between water and N supply and crop demand. A field experiment was conducted from 2016 to 2018 to evaluate whether reducing of irrigation and fertilizer N will reduce grain yield of wheat. There were two irrigation quotas (192 and 240 mm) and three fertilizer N rates (135, 180, and 225 kg N ha−1). The results showed that reducing irrigation to 192 mm and N rate to 180 kg N ha−1 reduced water uptake, water uptake efficiency, and N uptake of spring wheat as compared to local practice (i.e., 240 mm irrigation and 225 kg N ha−1 fertilizer). Whereas, it improved water and N utilization efficiency, and water and N productivity. Consequently, the irrigation and N rate reduced treatment achieved the same quantity of grain yield as local practice. The path analysis showed that interaction effect between irrigation and N fertilization may attributable to the improvement of grain yield with lower irrigation and N rate. The enhanced water and N utilization allows us to conclude that irrigation quota at 192 mm coupled with fertilizer N rate at 180 kg N ha−1 can be used as an efficient practice for wheat production in arid irrigation areas.

Study on the Exploitation Scheme of Groundwater under Well-Canal Conjunctive Irrigation in Seasonally Freezing-Thawing Agricultural Areas

The suitable groundwater exploitation scheme in freezing-thawing agricultural areas under the well-canal conjunctive irrigation conditions is confronted with two major challenges, which are computationally expensive local grid refinements along wells, and the model suitability problem in the freezing-thawing period. In this study, an empirical method for groundwater level prediction in the freezing-thawing period was developed and integrated with the local grid refinement groundwater model MODFLOW-LGR for the groundwater process prediction. The model was then applied to estimate the suitable groundwater exploitation scheme, including the size of well-irrigated area and the irrigation area of single well. The results showed that suitable size of well-irrigated area should be smaller than 15 × 106 m2, and the recommended irrigation area of single well as 15 × 104 m2 to 19 × 104 m2. The recommended layout parameters of groundwater exploitation were further used to plan the well-canal conjunctive irrigation scheme in Yongji irrigation district located in northern China. This study provides an important pilot example of the conjunctive use of groundwater and surface water in arid irrigation areas with a seasonal freezing-thawing period.

Drivers of carbon flux in drip irrigation maize fields in northwest China

BackgroundUnder the escalating threat to sustainable development from the global increase in carbon dioxide concentrations, the variations in carbon flux in the farmland ecosystem and their influencing factors have attracted global attention. Over the past few decades, with the development of eddy covariance technology, the carbon fluxes of farmlands have been determined in many countries. However, studies are very limited for drip irrigation maize the arid regions in northwestern China, which covers a large area where a mixed mode of agriculture and grazing is practiced.ResultsTo study the effects of drip irrigation on the net ecosystem productivity (NEE), ecosystem respiration (ER), gross primary production (GPP) and net biome productivity (NBP) in the arid regions of northwestern China, we measured the carbon flux annually from 2014 to 2018 using an eddy covariance system. Our results showed that the maize field carbon flux exhibited single-peak seasonal patterns during the growing seasons. During 2014–2018, the NEE, ER and GPP of the drip-irrigated maize field ranged between − 407 ~ − 729 g C m−2, 485.46 ~ 975.46 g C m−2, and 1068.23 ~ 1705.30 g C m−2. In four of the 5 study years, the ER released back to the atmosphere was just over half of the carbon fixed by photosynthesis. The mean daily NEE, ER and GPP were significantly correlated with the net radiation (Rn), air temperature (Ta), leaf area index (LAI) and soil moisture (SWC). The results of path analysis showed that leaf area index is the main driving force of seasonal variation of carbon flux. When harvested removals were considered, the annual NBP was − 234 g C m−2, and the drip-irrigated maize field was a carbon source.ConclusionsThis study shows the variation and influencing factors of NEE, ER and GPP in the growth period of spring maize under film drip irrigation in arid areas of northwest China. The ecosystem was a carbon sink before maize harvest, but it was converted into a carbon source considering the carbon emissions after harvest. The variation of carbon flux was influenced by both environmental and vegetation factors, and its leaf area index was the main driver that affects the seasonal variation of carbon flux.

The comparison of different irrigation methods on yield and water use efficiency of the jujube

Water shortage restricts the development of jujube plantation in southern Xinjiang, and the application of water–saving irrigation technology is the key to solve this problem. This study investigated the response of irrigation water use efficiency to various irrigation technologies (vertical tube irrigation and surface drip irrigation) and jujube yield and quality, and to choose a suitable irrigation method for Hui–jujube trees planting. The field experiment was conducted over 2 years. Vertical tube irrigation was implemented with three levels of water pressure by using water pressure heads 0.8, 1.0, and 1.2 m. Additionally, surface drip irrigation was used as a control, and four treatments were used in total. The results indicated that vertical tube irrigation helped save approximately 37–70% of water, and its water use efficiency was 1.4–4.3 times that of surface drip irrigation. Compared with Hui–jujube trees watered by drip irrigation, those watered by vertical tube irrigation had slightly higher yield and decreased fruit cracking (25–83%). Moreover, the sugar–acid ratio increased significantly (P < 0.05). Besides, the continuous water supply used in vertical tube irrigation allowed the maintenance of relatively stable SWC in the main root layer (20–60 cm), can provided a good soil–water–air environment for jujube growth. Vertical tube irrigation saved water primarily because it sends water directly to the main root layer through the emitters buried in the soil, reducing the evaporation of water in the upper soil layer. The irrigation water amount of vertical tube irrigation was proportional to the water supply pressure head. Water use efficiency was the highest under the lowest water supply pressure (water pressure head 0.8 m). The present findings provide a scientific basis for the application of vertical tube irrigation in arid areas.

No tillage and previous residual plastic mulching with reduced water and nitrogen supply reduces soil carbon emission and enhances productivity of following wheat in arid irrigation areas

Abstract No tillage, optimal nitrogen and irrigation supply levels, and crop rotation are promising strategies for reducing soil carbon emission, and plastic mulching is an important measure to improve crop productivity in arid regions. However, the effect of no tillage and plastic mulching combined with optimum management of water and nitrogen on soil carbon emission has not been tested. A field experiment was carried out in 2016–2018, to evaluate how no tillage, reduced the levels of irrigation and nitrogen affect crop yield, water use, and soil carbon emission of following spring wheat after plastic-mulched maize. A sustainability evaluation index was analyzed via integrating key parameters related to yield performance, water use, and soil carbon emission characteristics. Our results show that no tillage with previous residual plastic mulching, reduced irrigation, and reduced nitrogen application increased yield and water use efficiency of following wheat, but decreased soil carbon emission. From the 3-year average, no tillage and previous residual plastic mulching combined with the reduction of 20 % in both irrigation and nitrogen levels (i.e., the integrated system), increased grain and energy yields of following wheat by 13.7 and 7.8 %, respectively, compared to conventional tillage with conventional high levels of irrigation and nitrogen (i.e., the control). Also, the integrated system improved grain and energy yields for water use efficiency by 7.2 and 4.0 %, respectively. The soil carbon emission with the integrated system was 31.7 % lower than that with the control treatment, and the integrated system reduced soil carbon emission for water use efficiency by 33.8 % compared to the control treatment. However, the integrated system had 65.1 % greater carbon emission efficiency than the control treatment. The integrated system had the highest sustainability index among all treatments. Therefore, no tillage with previous residual plastic mulching from the previous maize combined with a 20 % reduction in both irrigation and nitrogen levels is an optimal strategy for sustainable and effective production of wheat in arid Oasis irrigation regions.

Quantitative analysis of the driving factors for groundwater resource changes in arid irrigated areas

AbstractHow to quantify the impact of climate change and human activities on groundwater is not only a hot topic of current research but also a key point of water resource management in arid irrigated areas. Therefore, this paper analyzes the changes in the trends of land use, climate, and groundwater extraction in the Yanqi Basin in recent years and uses the distributed hydrological model MIKE‐SHE to quantitatively analyze the impacts of these three factors on groundwater resources. The results show that: 1. The Nash coefficients of the simulated and observed groundwater levels during the verification period are 0.84, 0.79 and 0.76; the correlation coefficient between the simulated and observed soil moisture is 0.86. Although there are some uncertainties in the simulation, the results prove that the model can be used to simulate arid irrigated areas. 2. The effects of these three factors on groundwater levels are 5, 12.5 and 82.5%, respectively, and have caused the regional average groundwater level to decrease by a maximum of 0.07, 0.23 and 1.79 m, respectively. The effects of these three factors on the interactions between surface water and groundwater were 7.04, 3.63 and 89.33%. Groundwater extraction has become the main influencing factor of regional groundwater resources changes due to its more direct influence. 3. The influence of groundwater extraction has a strong spatial distribution characteristic and 10% of the study area has been greatly impacted by the groundwater extraction. Base on the above results, integrating multidisciplinary knowledge to establish the relationship between ecological environment and groundwater changes can provide strategies for the sustainable development of groundwater.

Water Use Conflict and Coordination between Agricultural and Wetlands—A Case Study of Yanqi Basin

Increased groundwater extraction leads to the decrease of the extent of wetlands due to the implementation of a water-saving transformation project in an arid irrigation area. The application of integrated mitigation tools and strategies in China have increasing significance. In this study, an integrated approach (SWAT-MODFLOW) was followed; it is based on a soil and water assessment tool (SWAT) coupled with a modular three-dimensional finite difference groundwater model (MODFLOW). Recharge and evaporation values were estimated by SWAT and were then used to simulate groundwater in a MODFLOW model. Calibration (over the years 2000–2010) and validation (over the years 2010–2016) were performed, based on observed groundwater-level data; results showed that the combined SWAT-MODFLOW provides more accurate simulation and prediction of the dynamic changes of surface water and groundwater in irrigation areas than results from individual MODFLOW models. This method was applied to the Yanqi Basin, which is one of the most appropriate arid agricultural basins for modeling lake wetland and groundwater in China. The correlation coefficients (R2) between the simulated and real groundwater level are 0.96 and 0.91 in SWAT-MODFLOW and MODFLOW, respectively. With the gradual increase in the extraction to 248%, 0.62 × 108 m3 of groundwater discharged into the lake became −2.25 × 108 m3. The lake level drops 1.3 m compared with the current year, when the groundwater exploitation increases by 10 × 108 m3/year. Overall, the results of the coupling model offer scientific evidence for agricultural water management and lake recovery, so as to enhance the water use coordination.

Effects of oxygenated brackish water on germination and growth characteristics of wheat

The long-term utilization of brackish water for irrigation in arid areas will decrease the oxygen content required for root growth, leading to the deterioration of soil environment in the root zone and the inhibition of plant growth. This study investigated the effects of oxygenated brackish water on the physiological characteristics of seed germination and seedling growth characteristics of spring wheat. The dissolved oxygen (DO) of 20 mg·l−1 in brackish water had a significant promotion effect on the seed germination and seedling growth. Specifically, at this DO concentration of 20 mg·l−1, the germination rate, germination potential, germination index, vigor index, and plant height on the 23rd day after sowing of wheat seeds were significantly higher than those of brackish water treatment (CK). Furthermore, compared with CK, the α-amylase activity in wheat seeds was significantly increased. Germination rate could be used as the quantitative evaluation index for wheat seed germination under the condition of oxygenated brackish water irrigation. According to the relationship between germination rate and DO concentration, the DO concentration with the maximum germination rate was 19 mg·l−1. During the wheat seedling growth period, compared with CK, the oxygenated brackish water with DO concentration of 20 mg·l−1 significantly increased the contents of soluble sugar and soluble protein in the leaves, whereas significantly decreased the proline content. Soluble sugar content was selected as the quantitative evaluation index for wheat seedling growth. The electrical conductivity and the activities of alkaline phosphatase and nitrate reductase in the root zone soil were significantly influenced. Thus, the oxygenation of brackish water with appropriate DO concentration could effectively improve the salt stress caused by brackish water irrigation. These results provide an effective method for the safe and efficient utilization of brackish water.

Comparison of different irrigation methods to synergistically improve maize’s yield, water productivity and economic benefits in an arid irrigation area

Water scarcity is everywhere and more prominent in arid and semi-arid regions. Moreover, water allocation for irrigation is hit by other economic sectors for low per capita profit. It is inevitable to extend higher-efficient irrigations to replace conventional border irrigation. A three-year field experiment was conducted to examine the effects of different irrigation methods on maize’s water use and economics in the Hetao Irrigation District of China. Taking 525-mm border irrigation as the control, furrow and drip irrigations at three water levels were implemented. Furrow irrigation included 100 % (450 mm), 80 % (360 mm) and 60 % (270 mm) of the recommended level, while three threshold values of soil matric potential: −10 kPa, −30 kPa, and −50 kPa, were used to trigger drip irrigation. The grain yield, ETc (water consumption for the whole growing season), ETcs (water consumption during a special growth stage), and water productivity were affected significantly by the irrigation methods and water levels. The average ETc of border, furrow and drip irrigations was 537.4 mm, 401.8–514.4 mm, and 306.6–496.2 mm for different levels, respectively. On average 10 % of the irrigation water was lost through deep percolation under border irrigation, while 10.5–29.0 mm of groundwater contributed to ETc under drip irrigation with −50 kPa. The higher Kwc (water consumption coefficient) was observed in R3-R6 (Milk-Maturity) stages under drip than border and furrow irrigations. The lower Ky (yield response factor) of drip (0.68) than furrow (0.82) indicated the lesser reduction in yield induced by the decreased ETc under drip irrigation. The 360-mm furrow irrigation obtained a comparable grain yield and net profit with the control, but reduced water application by 31 %. Drip irrigation at −30 kPa enhanced yield by 15 %, increased net profit by 23 %, and reduced water application by 57 %. Thus, drip irrigation at −30 kPa is recommended as the priority to replace border irrigation for maize production in the study area. If drip irrigation is unavailable, a 360-mm furrow irrigation is also an alternative to reduce water application without compromising benefit.

A novel regional irrigation water productivity model coupling irrigation- and drainage-driven soil hydrology and salinity dynamics and shallow groundwater movement in arid regions in China

Abstract. The temporal and spatial distributions of regional irrigation water productivity (RIWP) are crucial for making decisions related to agriculture, especially in arid irrigated areas with complex cropping patterns. Thus, in this study, we developed a new RIWP model for an irrigated agricultural area with complex cropping patterns. The model couples the irrigation- and drainage-driven soil water and salinity dynamics and shallow groundwater movement in order to quantify the temporal and spatial distributions of the target hydrological and biophysical variables. We divided the study area into 1 km × 1 km hydrological response units (HRUs). In each HRU, we considered four land use types: sunflower fields, wheat fields, maize fields, and uncultivated lands (bare soil). We coupled the regional soil hydrological processes and groundwater flow by taking a weighted average of the water exchange between unsaturated soil and groundwater under different land use types. The RIWP model was calibrated and validated using 8 years of hydrological variables obtained from regional observation sites in a typical arid irrigation area in North China, the Hetao Irrigation District. The model simulated soil moisture and salinity reasonably well as well as groundwater table depths and salinity. However, overestimations of groundwater discharge were detected in both the calibration and validation due to the assumption of well-operated drainage ditch conditions; regional evapotranspiration (ET) was reasonably estimated, whereas ET in the uncultivated area was slightly underestimated in the RIWP model. A sensitivity analysis indicated that the soil evaporation coefficient and the specific yield were the key parameters for the RIWP simulation. The results showed that the RIWP decreased from maize to sunflower to wheat from 2006 to 2013. It was also found that the maximum RIWP was reached when the groundwater table depth was between 2 and 4 m, regardless of the irrigation water depth applied. This implies the importance of groundwater table control on the RIWP. Overall, our distributed RIWP model can effectively simulate the temporal and spatial distribution of the RIWP and provide critical water allocation suggestions for decision-makers.

Co-circulation of Toscana virus and Leishmania infantum in a focus of zoonotic visceral leishmaniasis from Central Tunisia

In the Mediterranean basin, sand flies are vectors of Leishmania parasites and phleboviruses affecting humans and animals. In this study, we aimed to investigate phlebovirus and Leishmania parasites circulating in a focus of zoonotic visceral leishmaniasis (ZVL) located in a highly irrigated area within the arid Central Tunisia, known mainly to be endemic for zoonotic cutaenous leishmaniasis (ZCL) caused Leishmania major and transmitted by Phlebotomus papatasi. Sand flies were collected using CDC light traps in the village of Saddaguia, an emergent focus of ZVL located in Central Tunisia during September-October 2014, 2015, and 2016. Pools of live female sand flies were screened for phleboviruses and Leishmania by nested PCR in the polymerase gene and kinetoplast minicircle DNA, respectively. Dead sand flies were identified morphologically to species level. Sand flies of the subgenus Larroussius mainly Phlebotomus perfiliewi, Phlebotomus perniciosus, and Phlebotomus longicuspis were predominant in this ZVL focus compared to P. papatasi. A total of 1932, 1740, and 444 sand flies were tested in 2014, 2015 and 2016, respectively. Pathogen screening performed on 4116 sand flies distributed in 148 pools revealed the presence of Leishmania infantum and Toscana virus. The minimum infection rates of sand flies with TOSV in 2014, 2015, and 2016 were 0.05%, 011%, and 0.22%, respectively. The minimum infection rates of sand flies with L. infantum in 2014, 2015, and 2016 were 0.25%, 012%, and 0.79%, respectively. No L. major was detected during the 3-years investigation in this ZVL focus. Our results showed clearly the endemic co-circulation of TOSV and L. infantum in this emergent ZVL focus. However, no co-infection of TOSV and L. infantum was detected in any of the sand fly pools investigated during the three years period. TOSV was isolated from positive pools in 2015. Phylogenetic analysis showed that the Tunisian strains of TOSV belonged to the sublineage A. Based on the present findings, our results provided strong evidence that TOSV and L. infantum are transmitted by the same predominant sand fly species of the subgenus Larroussius, and subsequently, humans and dogs could be co-infected through co-infected or successive infected bites. Our results showed clearly that the development of irrigation in arid areas contributed significantly to the establishment of stable transmission cycles of L. infantum and TOSV and subsequently to the emergence of a ZVL focus within this arid bio-geographical area characterized by the presence of multiple foci of ZCL located outside the study site. Thus, more studies are needed to better understand the impact of RNA viruses shared by vectors and reservoir hosts of L. infantum on the development of zoonotic visceral leishmaniasis.

A sustainable irrigation water management framework coupling water-salt processes simulation and uncertain optimization in an arid area

Field irrigation water management depends on interactions among crop yield, soil water/salt and groundwater/salt in arid irrigation area with shallow-saline groundwater. This paper presents a novel uncertainty simulation-optimization framework for irrigation water allocation and sustainable agricultural environment, which integrates simulation of physical processes of soil-groundwater water and salt balance into an uncertainty-based optimization model. The impacts of crop evapotranspiration, soil water and salt and groundwater levels are interactively involved in the simulation model. Uncertainties (economic and crop parameters, available water amount) presented as fuzzy boundary intervals and probability distribution functions are considered in the optimization model. This field irrigation water allocation framework emphasizes the role of field soil water and salt movement processes to decision-making of irrigation water allocation. Then, the proposed simulation-optimization framework was applied to a case study in the Hetao Irrigation District, an arid area of northwest China where soil salinity is a serious environmental problem induced by irrigation and shallow groundwater. Therefore, optimal irrigation water allocation solutions can be generated for providing decision makers with reliable decision options where the maximum system benefits resulting from sustainable agricultural production are desired. Furthermore, the results can support analysis of interrelationships among system benefits, water allocation planning and groundwater depth, soil salt content constraints. Scenario analysis (groundwater table depth (GTD) = 1, 1.5, 2, 2.5, 3 m and no groundwater exchange consideration) showed that the maximum net benefit could be [27469, 44818] Yuan with the groundwater table depth of 1.5 m. Also, the irrigation water allocation changed when the salt constraint was considered, which indicates that the results obtained by the developed framework can alleviate soil salinization to a certain degree. Therefore, this framework can provide more effective information for the irrigation water management and soil salinization control, which is meaningful for the sustainable development of irrigation agriculture.

Using collector-drainage water in saline and arid irrigation areas for adaptation to climate change

The paper presents data of scientific research on the conditions of the Bukhara oasis of Uzbekistan reducing the salinity of collector-drainage water through water plants Lemna minor, Azolla caroliniana, Eichhornia crassipes and scientific and practical recommendations for the irrigation of cotton biologically purified collector-drainage waters. A decrease in the salinity of collector-drainage water with a salinity of 3-5 g/l was achieved with the help of aquatic plants Lemna minor and Azolla caroliniana, using them as an additional source of water for irrigation of cotton variety Bukhara-102, a high harvest of raw cotton, as well as saved river water and prevented environmental pollution.

New perspective about application of extended Budyko formula in arid irrigation district with shallow groundwater

Budyko’s treatment of the long-term water balance of watersheds was based on the competition between water availability and energy supply. It assumes, in the long-term, that precipitation is the only source of water availability for evapotranspiration while the changes in soil water storage are negligible. For arid irrigation areas with shallow water tables, however, groundwater also can supply crop water demand in addition to irrigation and precipitation. In this study, we present a new Budyko formula considering seasonal groundwater uptake and soil water storage changes estimated by Aver’yanov’s equation and abcd model, respectively. The use of groundwater depths rather than the variation of groundwater levels makes it more reasonable to estimate seasonal groundwater consumption. For the application of the Budyko equation in unsteady state areas, equivalent precipitation was designed to take the place of precipitation as water availability. With the newly defined water availability, the relationship between evapotranspiration ratio and aridity index was described successfully by Budyko curves, otherwise the points exceeded Budyko domain with only precipitation and irrigation considered. Furthermore, for agricultural irrigation areas, the variation of seasonal ω is supposed to be affected by vegetation coverage (denoted by NDVI). Overall, it is possible to estimate regional actual seasonal and annual evapotranspiration for irrigation areas with shallow groundwater using the extended Budyko models. This new method can play significant role in water management in arid and semiarid agricultural regions.

Influence of mulched drip irrigation on landscape scale evapotranspiration from farmland in an arid area

Water-saving irrigation measures in arid areas affect evapotranspiration (ET) processes while conserving water. Mulched drip irrigation is considered the most efficient irrigation method because it distributes water uniformly in the soil, restricts deep percolation, and minimizes unproductive evaporation from soil. The effect of mulched drip irrigation on farmland ET during the growing season at a landscape scale remains unclear, despite being vital for developing optimal water resource management strategies in arid areas. To compare the effects of mulched drip irrigation and mulched border irrigation on ET, based on Landsat satellite imagery (2007–2009 with mulched border irrigation, and 2014–2016 with mulched drip irrigation), an improved Surface Energy Balance Algorithm for Land (SEBAL) model was used to evaluate ET for the two periods of an oasis at Sangong River Basin in the arid region of Northwest China. The results show that daily ET rates from farmland managed under mulched drip irrigation were on average 0.2–1 mm.d−1 higher than under mulched border irrigation between June and August. Correspondingly, the net radiation flux (R) increased 73.32 W·m-2 on average, and R was found to be the main determinant of the ET differences. Meanwhile, the average land surface albedo decreased by 20%, and negatively correlated with R (P < 0.05), indicating that the land surface albedo was the main factor affecting R. Furthermore, the Normalized Difference Vegetation Index (NDVI) exhibited a significant correlation with land surface albedo. More importantly, the Temperature–Vegetation Dryness Index (TVDI) under mulched drip irrigation was found to be approximately 21% lower than that under mulched border irrigation, indicating that the soil moisture conditions of the farmland under mulched drip irrigation was significantly improved compared to mulched border irrigation. Namely, less water stress resulted in better developed canopy of the crops, which in turn captured more radiation and thus increased ET. In the end, the observed increases in landscape-scale ET under mulched drip irrigation in arid area resulted from enhanced productivity of the crops due to lessened drought stress.

Experimental Study on Productivity of Different Designs of Solar Stills in Hot Climatic Conditions

Because of the large increase in energy and water demand for agriculture, industry and human needs, and the increase in water pollution problems due to urbanization, industry and human activities, the demand for potable water has increased. Solar desalination is an alternative approach to save energy and converting saltwater into high-quality drinking water using solar energy. This work aims to design, manufacture, and test two types of solar still images (i.e. single slope and transparent tent) in order to improve their heat absorption and thereby improve efficiency under the prevailing hot climatic conditions of Al-Medina Al-Monawra. Accordingly, solar energy has been used for distillation purposes for saltwater purification to be used for drinking and irrigation in arid areas. Although solar devices are still simple in design, their values and advantages are very high. It also relies solely on renewable energy sources that are clean, free and unpolluted. In addition, economic analysis and comparisons of water productivity between the single slope solar still and the transparent tent have been presented. The results have indicated that the productivity of water per square meters per day for the transparent tent solar still is higher than the one of the single-slope solar still by about 6%. From economic analysis, the recovery period for both systems has been found to be about 3.5 years.