Quantification of irrigation water transport processes in ZiZiphus jujuba garden using water stable isotopes

ZiZiphus jujuba,which is native to China,has become one of the main crops widely planted in the western Loess Plateau because of its drought and flood-tolerance,adaptability,and higher nutritional value of the fruit.The irrigation water infiltration in Z.jujuba gardens is complex,and understanding its mechanisms is essential for efficient water use and sustainable agriculture.This knowledge helps ensure the long-term success of jujuba cultivation.This paper describes a field experiment that investigates the infiltration process of irrigation water from Z.jujuba garden and quantifies the contribution of irrigation water to soil water at different depths using the MixSIAR model.According to the FC(Field water holding Capacity)of Z.jujuba,irrigation experiments with three volumes of 80%FC,60%FC,and 40%FC are set up in this study.The study finds that water retention is better in Z.jujuba garden soils with a higher proportion of coarse gravel in the soil particle composition.Soil water content exhibits a gradient change after irrigation,with deeper wetting front transport depth observed with increased irrigation water.Additionally,there is correlation between soil temperature and soil water content.The soil water in Z.jujuba garden generally exhibits a preferential flow signal in the 0-40 cm range.Below 40 cm,a piston flow pattern dominates.The rate of soil water infiltration increases with the amount of irrigation water.In the 0-40 cm range of the soil vertical profile,irrigation water was the main contributor to soil water.Z.jujuba demonstrated flexibility in water uptake,primarily absorbing soil water at depths of 0-40 cm.For optimal growth of Z.jujuba at this stage,40%FC irrigation is recommended.The results are expected to be valuable future irrigation practices and land use planning for Z.jujuba garden in arid zones,supporting sustainable agricultural development and water management.

Reform of the Irrigation Sector and Creation of Functional and Sustainable Irrigation Water Users Associations (AUEI) in Niger: Capitalization of the Experience of the Konni AHA

During the 1980s, as part of a policy of liberalization, following budgetary cuts linked to the implementation of structural adjustment programs, management responsibilities for AHAs were transferred from ONAHA to cooperatives concerned. Due to lack of financial resources, but also because of poor management, everywhere in Niger we are witnessing an accelerated deterioration of the irrigation infrastructure of hydro-agricultural developments. Institutional studies carried out on this situation led the State of Niger to initiate a reform of the governance of hydro-agricultural developments, by streng-thening the status of ONAHA, by creating an Association of Irrigation Water Users (AUEI) and by restructuring the old cooperatives. Indeed, this research aims to analyze the creation of functional and sustainable Irrigation Water User Associations (AUEI) in Niger in a context of reform of the irrigation sector, and based on the experience of the Konni AHA. It is based on a methodological approach which takes into account documentary research and the collection of data from 115 farmers, selected by reasoned choice and directly concerned by the management of the irrigated area. The data collected was analyzed and the results were analyzed using the systemic approach and the diagnostic process. The results show that the main mission of the AUEI is to ensure better management of water, hydraulic equipment and infrastructure on the hydro-agricultural developments of Konni. The creation of the Konni AUEI was possible thanks to massive support from the populations and authorities in the implementation process. After its establishment, the AUEI experienced a certain lethargy for some time due to the rehabilitation work of the AHA but currently it is functional and operational in terms of associative life and governance. Thus, the constraints linked to the legal system, the delay in the completion of the work, the uncertainties of access to irrigation water but also the problems linked to the change in mentality of certain ONAHA agents constitute the challenges that must be resolved in the short term for the operationalization of the Konni AUEI.

Analysis and Evaluation of Heavy Metal Environmental Quality of Irrigation Water in Vegetable Farmlands of Shandong Province

[Objective] The aim was to evaluate heavy metal environmental quality of irrigation water in vegetable farmlands of Shandong Province. [Method] Heavy metal contents including Hg,Cd,As,Cr (+6),Pb,Cu and Zn in irrigation water of main vegetable farmlands of Shandong Province were investigated by randomly sampling,and the environmental quality conditions of these heavy metals were evaluated by methods of single quality index and complex quality index. [Result] The results showed that the average contents of heavy metals in irrigation water of Shouguang,Laiyang,Jinxiang and Zhangqiu were all far lower than the limit values prescribed by 'Farmland Environmental Quality Evaluation Standards for Edible Agricultural Products' (HJ332-2006),and no heavy metal was found beyond the limit value in every sample. The single quality indices of the 7 elements in the studied 4 places were all lower than 0.5. The comprehensive quality index of the seven elements was 0.317 8 in Shouguang,0.320 4 in Laiyang,0.232 6 in Jinxiang,and 0.260 7 in Zhangqiu. The environmental quality of irrigation water in the studied four places were all set at the first class. [Conclusion] The environmental quality of irrigation water in the 4 places belonged to clean level and were fit for the plantation of no pollution vegetables.

Comprehensive Evaluation on the Irrigation Water Quality in Turpan City Based on Matter Element Analysis Method

Matter-element analysis method was used to construct the comprehensive matter-element model for the evaluation of the quality of various kinds of irrigation water in Turpan City to evaluate the quality of irrigation water（such as river water,spring water, Karez well water, pumped well water） in Turpan City, Xinjiang. The results showed that the quality of the irrigation water was the best in October,which was in Grade I or Grade 2; in May, the quality of some of the irrigation water became poorer to Grade II, which was easy to soil salinization; in March, the detected qualities of the water samples water from the Meiyaogou basin were all in Grade IV, which was not suitable for farmland irrigation. The comparison on the evaluation results of matter-element analysis and fuzzy evaluation method showed that the results of the 2 methods were almost consistent with each other, and showed good uniformity.

Effect of Irrigation Water Quality on Soil Hydraulic Conductivity

The effect of irrigation water quality on unsaturated hydraulic conductivity (HC) of undisturbed soil in field was studied.Results show that within the operating soil suction range (0-1.6 KPa) of disc permeameters,the higher the electric conductivity (EC) of irrigation water,the higher the soil HC became.The soil HC doubled when EC increased from 0.1 to 6.0ds m^-1.High sodium-adsorption ratio(SAR) of irrigation water would have an unfavorable effect on soil HC.Soil HC decreased with the increasing of SAR,especially in the case of higher soil suction.An interaction existed between the effects of EC and SAR of irrigation water on soil HC.The HC of unsaturated soil dependent upon the macropores in surface soil decreased by one order of magnitude with 1 KPa increase of soil suction.In the study on the effect of very low soluble salt concentration (EC=0.1 ds m^-1 of irrigation water on soil HC,soil HC was found to be lowered by 30% as a consequence of blocking up of some continuous pores by the dispersed and migrated clay particles.Nonlinear successive regression analysis and significance test show that the effects of EC and SAR of irrigation water on soil HC reached the extremely significant level.

Irrigation Water Use Efficiency of Farmers and Its Determinants: Evidence from a Survey in Northwestern China

Irrigation water shortage is becoming an increasingly serious problem in agricultural production. In this case, it is very important for policy makers to take measures to improve irrigation water use efficiency, especially in the water-scarce areas. In this paper, the data envelopment analysis （DEA） techniques, based on the concept of input-specific technical efficiency were used to develop farm-level technical efficiency measures and sub-vector efficiencies for irrigation water use. The Tobit regression technique was then adopted to identify the factors that influence irrigation water efficiency differentials under the shortage of water resources. Based on a sample data of 432 wheat farmers in northwestern China, our experimental results of the DEA analysis showed the average technical efficiency of 0.6151. It suggested that wheat farmers could increase their production by as much as 38.49% by using inputs more efficiently. Further, the mean irrigation water efficiency of 0.3065, suggested that wheat farmers could produce the same quantity of wheat using the same quantity of inputs but with 69.35% less water. The results of the Tobit regression analysis showed that the farmer＇s age, income, education level, and the farm size tended to affect the degree of irrigation water efficiency positively, and the channel conditions and different irrigation methods made a significant impact on irrigation water use efficiency. Furthermore, the arrangements of exclusive water property rights and competitive water price mechanism have effectively encouraged the water saving behavior of farmers. These results are valuable for policy makers since it could help to guide policies towards high irrigation water use efficiency.

Fruit Yield and Quality, and Irrigation Water Use Efficiency of Summer Squash Drip-Irrigated with Different Irrigation Quantities in a Semi-Arid Agricultural Area

Fruit yield, yield components, fruit mineral content, total phenolic content, antioxidant activity and irrigation water use efifciency （IWUE） of summer squash responses to different irrigation quantities were evaluated with a ifeld study. Irrigations were done when the total evaporated water from a Class A pan was about 30 mm. Different irrigation quantities were adjusted using three different plant-pan coefifcients （Kcp, 100% （Kcp1）, 85% （Kcp2） and 70% （Kcp3））. Results indicated that lower irrigation quantities provided statistically lower yield and yield components. The highest seasonal fruit yield （80.0 t ha-1） was determined in the Kcp1 treatment, which applied the highest volume of irrigation water （452.9 mm）. The highest early fruit yield, average fruit weight and fruit diameter, length and number per plant were also determined in the Kcp1 treatment, with values of 7.25 t ha-1, 264.1 g, 5.49 cm, 19.95 cm and 10.92, respectively. Although the IWUE value was the highest in the Kcp1 treatment （176.6 kg ha-1 mm-1）, it was statistically similar to the value for Kcp3 treatment （157.1 kg ha-1 mm-1）. Total phenolic content and antioxidant activity of fruits was higher in the Kcp1 （44.27 μg gallic acid equivalents （GAE） mg-1 fresh sample） and in the Kcp2 （84.75%） treatments, respectively. Major （Na, N, P, K, Ca, Mg and S） and trace （Fe, Cu, Mn, Zn and B） mineral contents of squash fruits were the highest in the Kcp2 treatment, with the exception of P, Ca and Cu. Mineral contents and total phenolic content were signiifcantly affected by irrigation quantities, but antioxidant activity was not affected. It can be concluded that the Kcp1 treatment was the most suitable for achieving higher yield and IWUE. However, the Kcp2 treatment will be the most suitable due to the high fruit quality and relatively high yield in water shortage conditions.

Effect of Sulphur in Rainfall, Irrigation Waterand Perco colating Water on Soil Sulphur in Jiangxi Province

Ten rainfall and irrigation water-collecting posts were set up in different ecotype districts of JiangxiProvince, China, to quarterly measure S content in rainfall and irrigation water. A rainwater chemicalcomposition- collecting device was used to collect the sulphur in rainfall land the amount of sulphur adsorbedon the resin column in the device was determined. The soil percolating water was gathered using 6 lysimeters,built up according to the profile sequence of the red soil derived from red sandstone and the red soil derivedfrom Quaternary red clay, separately. On the lysimeters peanuts, soybean and radish were grown in rotation.Two treatments were designed: without S addition and with S addition at a rate of 14 kg S ha-1. The SO24contents in rainfall, irrigation water and soil percolating water were determined by the turbidimetry.The results in 1997 showed that the average annual S content in rainwater was 28.13 kg S ha-1, theaverage S content in irrigation water was 1.7 mg S L-1 , and the average content of in soil percolationwater was 2.30 kg S ha-1 year-1 and 4.70 kg S ha-l year-1 in treatments without and with sulphurapplication, respectively. In Jiangxi Province, apart from the losses by runoff and leaching, the sulphur inrainfall available to crops is 7.3 kg S ha-1 year-1 and additional S application is required. When rice isgrown , however, irrigation water can supply 6.9 kg S ha-1, which, along with the sulphur in rainfall, canalmost meet the S requirement of one cropping of rice.

A study of groundwater irrigation water quality in south-central Bangladesh: a geo-statistical model approach using GIS and multivariate statistics

Southern Bangladesh＇s irrigation and drinking water is threatened by saline intrusion. This study aimed to establish an irrigation water quality index （IWQI） using a geostatistical model and multivariate indices in Gopalganj district, south-central Bangladesh. Groundwater samples were taken randomly （different depths） in two seasons （wet-monsoon and dry-monsoon）. Hydrochemical analysis revealed groundwater in this area was neutral to slightly alkaline and dominating cations were Na^＋, Mg^2＋, and Ca^2＋ along with major anions Cl^- and HCO3^-. Principal component analysis and Gibbs plot helped explain possible geochemical processes in the aquifer. The irrigation water evaluation indices showed： electrical conductivity （EC） 〉750 μS/cm, moderate to extreme saline; sodium adsorption ratio （SAR）, excellent to doubtful; total hardness （TH）, moderate to very hard; residual sodium bicarbonate, safe to marginal; Kelly＇s ratio 〉1; soluble sodium percentage （SSP）, fair to poor; magnesium adsorption ratio, harmful for soil; and IWQI, moderate to suitable. In addition, the best fitted semivariogram for IWQI, EC, SAR, SSP, and TH confirmed that most parameters had strong spatial dependence and others had moderate to weak spatial dependence. This variation might be due to the different origin/sources of major contributing ions along with the influence of variable river flow and small anthropogenic contributions. Furthermore, the spatial distribution maps for IWQI, EC, SSP, and TH during both seasons confirmed the influence of salinity from the sea; low-flow in the major river system was the driving factor of overall groundwater quality in the study area. These findings may contribute to management of irrigation and/or drinking water in regions with similar groundwater problems.

Characteristics of produced water during coalbed methane （CBM） development and its feasibility as irrigation water in Jincheng, China

Water resources are scarce in Jincheng. Huge quantities of water are pumped out in the dewatering course, and the disposal of CBM water is one of the most important problems during the extracting of CBM. Based on the data of CBM water production, chemical characteristics, the irrigational conditions for major crops, and China irrigation water standard, the feasibility of CBM water as irrigation water is discussed. The result shows the CBM water quality doesn＇t fully meet irrigation water quality standards in Jincheng, its high salinity and sodium adsorption ratio （SAR） in CBM water might affect crops growth and lead to yield loss, and can＇t be used as irrigation water directly, but with the treatment of the reverse osmosis （RO） to lower the salinity and SAR of CBM water, the CBM water can be used as irrigation water.

Estimation of the Economic Value of Irrigation Water in Jordan

Insight into the different values of water is essential to support rational decision making about policies, management and investments in the water sector. The main objective of this paper is to estimate an economic value of irrigation water in Jordan by choosing appropriate methodology fit with available data. The Residual Imputation Method （RIM） is used to determine the average economic value of irrigation water used in agriculture across crops. The results showed that the weighted average of water value used in field crops is JD 0.44 m＂3 and JD 1.23 m3 for vegetable crops and JD 0.23 m3 for fruit trees. The overall weighted average water value in irrigation is estimated with JD 0.51 m＂3. With regard to individual crops, cucumbers had the highest water values with about JD 6.05 m3, followed by string beans with JD 2.64 m3, and sweet pepper with JD 2.54 m3. The lowest returns per m3 were provided by squash, radish and hot pepper. For fruit tress banana has the highest water value JD 0.79 m3 and olive tress has the lowest with only JD 0.069 m3. The current practice of some banana producers is economically rational by installing Reverse Osmosis unit to irrigate banana, since water value is twice the desalination costs of one cubic meter. The estimated values represent the maximum price that farmers might be willing to pay for water under the current market conditions. Water subsidy distorts farmers＇ perception of water as a scarce and thus valuable resource. Low water prices are thus likely to engender excessive use. It is necessary to allow water prices to recover the real cost of water supply and to ensure financial sustainability of water utilities.

Investigation on the Quality of Irrigation Water in Southern Anhui and the Effects of Metal Elements in Irrigation Water on the Coke Sweet Aroma Style of Tobacco Leaves

[Objectives]The effects of metal elements in irrigation water in the tobacco areas of southern Anhui on the coke sweet aroma of tobacco leaves was determined.[Methods]53 representative areas for tobacco planting in southern Anhui were selected,and the quality of irrigation water,especially the content of metal elements,was investigated.[Results]The contents of micro(medium)elements in the irrigation water were too low to have a significant effect on the formation of the coke sweet aroma style of tobacco leaves.The contents of Mg,Ca and Zn were 0.7-8.0,<40 and 0.002-0.029 mg/L,respectively.The heavy metal contents of the irrigation water and other basic control items all met corresponding national standards.Furthermore,the tobacco planting experiment under controlled irrigation using paddy soil in the greenhouse proved that Zn was a negative correlation factor for forming the coke sweet aroma style of tobacco and the threshold value was≥10 mg/L in the irrigation water.Meanwhile,Mg was a positive correlation factor and the content of Mg to promote the coke sweet aroma style should be maintained at 40-90 mg/L.Ca and Mg had a synergistic effect,which was mainly appropriate for acid paddy soils.[Conclusions]This study improves the quality and yield of the coke sweet aroma of tobacco leaves,and has important theoretical and practical value for the formation of a popular agronomic control method.

Maximizing Irrigation Water Productivity by Optimizing Leaching Fraction

The importance of maximizing irrigation water productivity is increasing as the water resources still decreasing and deteriorating due to environmental interactions. An optimal irrigation water depth （including leaching water depth） was estimated in order to maximize water unit volume productivity by using the optimal leaching fraction （LF）, which is calculated by the new proposed model--unit yield ratio （UYR%） and irrigation depth ratio （IDP）. A computer program was constructed to apply this model for several crops irrigated by two water resources--river and well. The water salinity of river was 1.1 dS/m and the well salinity was 3.85 dS/m. The results showed that there is an optimal leaching requirement （LR） value for each crop irrigated by any water resource. The maximum UYR% of the alfalfa irrigated by saline well water was 58.45% with the optimal LF = 0.4, while the maximum UYR% of the bean irrigated by river water was 78.58% with the optimal LR = 0.2. The optimal LF is saving water by increasing the productivity of irrigation water unit volume, especially when using saline irrigation water, for example, an increase of IDP for alfalfa by only 20%, followed by an increase of UYR% about 47.5% （from 12% to 57%） by increasing LF from 0.1 to 0.3.

Development of a concentration method for detection of tobacco mosaic virus in irrigation water

Tobacco mosaic virus(TMV) causes significant yield loss in susceptible crops irrigated with contaminated water. However, detection of TMV in water is difficult owing to extremely low concentrations of the virus. Here, we developed a simple method for the detection and quantification of TMV in irrigation water. TMV was reliably detected at concentrations as low as 10 viral copies/μL with real-time PCR. The sensitivity of detection was further improved using polyethylene glycol 6000(PEG6000, MW 6000) to concentrate TMV from water samples. Among the 28 samples from Shaanxi Province examined with our method, 17 were tested positive after virus concentration. Infectivity of TMV in the original water sample as well as after concentration was confirmed using PCR. The limiting concentration of TMV in water to re-infect plants was determined as 102 viral copies/mL. The method developed in this study offers a novel approach to detect TMV in irrigation water, and may provide an effective tool to control crop infection.

Implications of future climate change on crop and irrigation water requirements in a semi-arid river basin using CMIP6 GCMs

Agriculture faces risks due to increasing stress from climate change,particularly in semi-arid regions.Lack of understanding of crop water requirement(CWR)and irrigation water requirement(IWR)in a changing climate may result in crop failure and socioeconomic problems that can become detrimental to agriculture-based economies in emerging nations worldwide.Previous research in CWR and IWR has largely focused on large river basins and scenarios from the Coupled Model Intercomparison Project Phase 3(CMIP3)and Coupled Model Intercomparison Project Phase 5(CMIP5)to account for the impacts of climate change on crops.Smaller basins,however,are more susceptible to regional climate change,with more significant impacts on crops.This study estimates CWRs and IWRs for five crops(sugarcane,wheat,cotton,sorghum,and soybean)in the Pravara River Basin(area of 6537 km^(2))of India using outputs from the most recent Coupled Model Intercomparison Project Phase 6(CMIP6)General Circulation Models(GCMs)under Shared Socio-economic Pathway(SSP)245 and SSP585 scenarios.An increase in mean annual rainfall is projected under both scenarios in the 2050s and 2080s using ten selected CMIP6 GCMs.CWRs for all crops may decline in almost all of the CMIP6 GCMs in the 2050s and 2080s(with the exceptions of ACCESS-CM-2 and ACCESS-ESM-1.5)under SSP245 and SSP585 scenarios.The availability of increasing soil moisture in the root zone due to increasing rainfall and a decrease in the projected maximum temperature may be responsible for this decline in CWR.Similarly,except for soybean and cotton,the projected IWRs for all other three crops under SSP245 and SSP585 scenarios show a decrease or a small increase in the 2050s and 2080s in most CMIP6 GCMs.These findings are important for agricultural researchers and water resource managers to implement long-term crop planning techniques and to reduce the negative impacts of climate change and associated rainfall variability to avert crop failure and agricultural losses.

Interactive effects of deficit irrigation and vermicompost on yield,quality,and irrigation water use efficiency of greenhouse cucumber

Water scarcity is the most significant barrier to agricultural development in arid and semi-arid regions.Deficit irrigation is an effective solution for managing agricultural water in these regions.The use of additives such as vermicompost(VC)to improve soil characteristics and increase yield is a popular practice.Despite this,there is still a lack of understanding of the interaction between irrigation water and VC on various crops.This study aimed to investigate the interaction effect of irrigation water and VC on greenhouse cucumber yield,yield components,quality,and irrigation water use efficiency(IWUE).The trials were done in a split-plot design in three replicates in a semi-arid region of southeastern Iran in 2018 and 2019.Three levels of VC in the experiments,i.e.,10(V_(1)),15(V_(2)),and 20 t/hm^(2)(V_(3)),and three levels of irrigation water,i.e.,50%(I_(1)),75%(I_(2)),and 100%(I_(3))of crop water requirement were used.The results showed that the amount of irrigation water,VC,and their interaction significantly affected cucumber yield,yield components,quality,and IWUE in both years.Reducing the amount of irrigation water and VC application rates reduced the weight,diameter,length,and cucumber yield.The maximum yield(175 t/hm^(2))was recorded in full irrigation using 20 t/hm^(2)of VC,while the minimum yield(98 t/hm^(2))was found in I_(1)V_(1)treatment.The maximum and minimum values of IWUE were recorded for I_(1)V_(3)and I_(3)V_(1)treatments as 36.07 and 19.93 kg/(m^(3)•hm^(2)),respectively.Moreover,reducing irrigation amount decreased chlorophyll a and b,but increased vitamin C.However,the maximum carbohydrate and protein contents were obtained in mild water-stressed conditions(I_(2)).Although adding VC positively influenced the value of quality traits,no significant difference was observed between V_(2)and V_(3)treatments.Based on the results,adding VC under full irrigation conditions leads to enhanced yield and IWUE.However,in the case of applying deficit irrigation,adding VC up to a certain level(15 t/hm^(2))increases yield and IWUE,after which the yield begins to decline.Because of the salinity of VC,using a suitable amount of it is a key point to maximize IWUE and yield when applying a deficit irrigation regime.

Spatial Patterns of Irrigation Water Withdrawals in China and Implications for Water Saving

By considering numerical features, spatial variation, and spatial association, the spatial patterns of China's irrigation water withdrawals in 2001 and 2010 were explored at the regional, provincial, and prefectural scales. In addition, an overlay analysis was used to develop specific water-saving guidance for areas under different levels of water stress and with different degrees of irrigation water withdrawals. It was found that at the regional scale, irrigation water withdrawals were highest in the Middle-Lower Yangtze River region in both years, while at the provincial scale, the largest irrigation water withdrawals occurred in Xinjiang. During 2001–2010, the total of irrigation water withdrawals decreased; however, in the Northeast region, especially in Heilongjiang Province, it experienced a dramatic increase. The spatial variation was largest at the prefectural scale, with an apparent effect. The spatial association was globally negative at the provincial scale, and Xinjiang was the only significant high-low outlier. In contrast, the association displayed a significant positive relationship at the prefectural scale, and several clusters and outliers were detected. Finally, it was found that the water stress in the northern part of China worsened and water-saving irrigation techniques urgently need to be applied in the Northeast region, the Huang-Huai-Hai Plain region, and Gansu-Xinjiang region. This study verified that a multi-scale and aspect analysis of the spatial patterns of irrigation water withdrawals were essential and provided water-saving advice for different areas.

Assessment of Irrigation Water Quality Parameters of Nyandungu Wetlands

The present paper sought to assess some physico-chemical parameters above permissible guidelines of irrigation water standard, the study was carried during establishment of Ecotourism Park. The field survey design was used and it was accompanied by laboratory tests to analyze the levels of physico-chemical parameters in both seasons (dry season and wet seasons) for water bodies as well as groundwater. The physical chemical parameters analysed were Sodium Adsorption Ratio (SAR), Soluble Sodium Percentage (SSP) Magnesium Adsorption Ratio (MAR) Kelly Index (KI) Total Hardness (TH), pH, the Electric conductivity (EC), Total Dissolved Solids (TDS). Our analyzed samples fall into permissible limit of irrigation water quality, the mean values of electrical conductivity were high. The knowledge from this study will be used in establishment of Nyandungu recreation park irrigating with water quality on gardens surrounding recreation park and local community.

Some Problems of Irrigation Water Management in Lower Cheliff Plain （Algeria）

In the Lower Cheliff Plain （northwestern of Algeria）, the waters resources are limited; the adoption of a rational approach in the management of irrigation water in the irrigated perimeter poses an inequality in the balance between supply and demand. The two surface water resources, Gargar and Merdjet Sidi Abed dams, do not satisfy the requirements of agriculture water. According to the National Office of the Irrigation and Drainage data, the quantity of allocated water is never distributed; the difference between allocated water and drop water can also exceed 20%, and then, another problem of management is that the water losses in the distribution can reach 20% again. The shortage irrigation water resource allocated has constrained the farmers to use groundwater. The chemical analysis of 56 simples to this water showed a significant chemical diversity in the compositions. There is a high salinity risk （C3 class） or very high risk （C4 class） of soil salinisation. A space chart distribution to the EC water probability to exceed 2.25 dS/m interpolated by the indicator kriging method showed that 78% of the groundwater surface presents a significant probability to exceed this limit. The average value of the SAR （sodium adsorption ratio） is lower than 10 that indicates a moderate risk of sodisation. This observation is in contradiction with the high values of the SAR measured in the soil solution. The approach of residual alkalinity （RSC） shows that a good number of drillings analyzed presents a positive sign RSC （RSC 〉 0）. This water presents a real danger of sodisation. They have a low salinity, which, for a farmer, does not present any danger.

Migration of Heavy Metal Elements in Reclaimed Irrigation Water-Soil-Plant System and Potential Risk to Human Health

[Objectives]To study the impact of heavy metal pollution of soil and plants during the process of reclaimed water for irrigation of green land in arid areas and the potential health risks to humans during use.[Methods]Taking Zhongwei City in Ningxia,a typical arid area,as the research area,the irrigation water,soil and green grass in the reclaimed water irrigation region and the original green water irrigation region were sampled,the heavy elements Hg,As,Zn,Pb,Cd,Cr were detected,and the Nemerow method,biological absorption coefficient,and health risk assessment were employed to evaluate the degree of soil pollution,plant absorption capacity,and human health risks.[Results]Compared with the original green water,the Hg,Cd,and Cr pollution of the reclaimed water irrigated green land was higher,the As,Zn,Pb pollution was lower,and the content of Hg and Cd was higher than the environmental background values of soil in Ningxia;the Cr content exceeded the risk intervention values of the first type of land in the Soil Environmental Quality—Risk Control Standard for Soil Contamination of Development Land(GB 36600-2018).Compared with the original green water irrigation region,it is found that the reclaimed water irrigation reduced the heavy metal pollution of the soil to a certain extent.The heavy metal content of tall fescue grass(Festuca arundinacea)in the reclaimed water irrigation region was Zn,Cr,Pb,As,Cd,and Hg from high to low;the order of the biological absorption coefficient was Cd>As>Zn>Pb>Hg>Cr;irrigation water exerted a certain effect on the content of heavy metals in plants and the biological absorption coefficient through the soil.Using the health risk assessment method recommended by Environmental Protection Agency of the United States of America(USEPA),it was found that the reclaimed water has the highest risk through the inhalation route,and the occupational population has a higher risk of skin contact with soil and plants.[Conclusions]This study is intended to provide data support and theoretical basis for the environmental safety risk research of the application of reclaimed water in arid areas to urban greening.