In order to analyze the distribution law and influencing factors of fertilizer concentration in the process of water and fertilizer integrated micro－spray belt operation，the effects of fertilizer type and pressure difference of fertilization tank on the pressure along the micro －spray zone and the concentration distribution of fertilizer solution were studied． The results show that when the length of the micro－spray belt is 40 meters，the pressure along the path gradually decreases，but the decrease is slower and slower at further distance; the greater pressure at the head of the pipe，the greater pressure difference between the first and the tail of the pipe，and the lower uniformity of the micro－spray zone． In the combination with the effective spray range of the micro－spray belt，the field of micro－spray belt has a suitable first working pressure ( the pressure of micro－spray belt in this study is 50～ 60 kPa) ． The concentration of N fertilizer ( easy soluble fertilizer) is obviously affected by the pressure difference of the fertilization tank． The trend of the concentration of P fertilizer ( insoluble fertilizer) is gentle，and the concentration changes sharply with time． In actual practice，the appropriate working pressure and the pressure difference between the fertilizer tanks shall be determined according to different fertilizers，and the appropriate spraying time should be selected to ensure the uniformity of fertilization and the amount of fertilizer applied．

To study the effects of groundwater depth on soil water change in the shallow buried area of Huaibei Plain in summer maize growth period, the field data of the Wudaogou Hydrological Experimental Station from 1992 to 2014 were analyzed, including 0-1.0m vertical soil moisture, groundwater depth (variation 1-3m) and meteorological data. By using regression analysis method, regression models of average water content and groundwater depth of 0.3-0.4, 0.4-0.5m, 0.5-0.6m, 0.6-0.8m, 0.8-1.0m and 0-1.0m soil layers were established. The results showed that the average water content of 0.3-0.4m, 0.4-0.5m, 0.5-0.6m, 0.6-0.8m, 0.8-1.0m and 0-1.0m soil layer was linearly negatively correlated with groundwater depth, and the goodness of fit were 0.632, 0.739, 0.788, 0.861, 0.834, and 0.780, respectively. This study could be of great significance for timely understanding of soil water dynamics, rationally regulating depth of groundwater table, and effectively improving the water use efficiency of field.

The effects of different planting densities on maize growth characteristics，yield，soil profile water distribution，and irrigation water utilization efficiency ( IWUE) and benefits were studied by field experiments of drip irrigation under film． With Limin 33 as the test crop， three treatments with planting densities of 75 000，82 500 and 90 000 plants per hm2 were set up． Leaf length and width，plant height，leaf area index，yield and its constituent elements，water content and utilization rate of maize were compared and analyzed． The results showed that the soil moisture content of the treatment of 75 000 plants per hm2 was the largest，while that of the treatment of 82 500 plants per hm2 was the smallest; the variation trend of soil moisture content in the 0～ 80 cm soil layer in each growing season was basically the same，which fluctuated with time; compared with the treatments of 75 000 and 90 000 plants per hm2 ，the water consumption of the treatment of 82 500 plants per hm2 was reduced by 82．04 and 74．23 m3 /hm2 ，respectively，and the irrigation water utilization efficiency was increased by 1．13 and 2．14 kg /m3 ; meanwhile，maize grew well and obtained higher yield and benefit; the planting density affected the growth，yield and irrigation water utilization efficiency of maize，and then affected the production efficiency． Under the experimental conditions，the suitable planting density was 82，500 plants per hm2 ，which could obtain better planting effect

A field experiment was carried out in the Taihu lake basin of China to investigate the effect of straw return on soil organic carbon and its components of paddy field under water－saving irrigation． The treatments included two irrigation methods，i．e． controlled irrigation( C) and flooding irrigation ( F) ，and two fertilization management modes，i．e． straw return( S) and non－straw return ( F) ． The study analyzed the dynamic changes of soil organic carbon and active organic carbon and the correlation between the components under different water carbon managements． The results showed that controlled irrigation accelerated the decomposition of soil organic carbon，and the combination with straw mulching promoted the accumulation of soil organic carbon in paddy field; under different fertilizer management conditions，the average values of soil organic carbon ( TOC) ，dissolved organic carbon ( DOC) and soil microbial carbon ( SMBC) in the rice season in the controlled irrigation paddy fields were reduced by 10%，1．8% and 7．9%，respectively，than those in the conventional irrigation paddy fields; compared with conventional water and fertilizer management ( FF) ，TOC and SMBC with straw mulching under controlled irrigation( CS) increased by 10．4% and 15．3%，respectively; there were significant positive correlations between DOC and TOC，SMBC and TOC in paddy soil under different water and carbon management modes; applying straw under water－saving irrigation was beneficial to increase soil organic carbon content and improve soil active carbon composition．

In order to explore the effect of applying desulfurization gypsum and biochar on water，thermal and salt of saline soil in Hetao irrigation area and the effect on crop yield to select reasonable improvement measures，a field positioning experiment was carried out in Hetao irrigation area of Inner Mongolia in 2018． Four treatments were set up in the experiment: conventional tillage ( CK) ，smashing ridge tillage ( F0) ，desulfurized gypsum with smashing ridge tillage ( F1) ，and biochar with smashing ridge tillage ( F2) ． The effects of different treatments on soil water holding capacity，soil temperature，conductivity and sunflower yield were analyzed． The results show that: F0，F1 and F2 can all reduce the bulk density of soil． By using VG model fitting analysis，it is found that the parameters of θs，θr，a and bulk density are negatively correlated，and the water holding capacity of F1 and F2 are all higher than that of CK． Compared with CK，F0，F1 and F2 treatments all reduce soil conductivity by 23．85%，28．80% and 32．11% on average，significantly increase sunflower yield ( p＜0．05) ，and increase grain yield by 130%，266% and 311%，respectively． The comprehensive analysis result shows that the application of desulfurized gypsum and biochar under the smashing ridge tillage condition can improve soil moisture and salt control ability and promote crop yield，and the effect is more significant than that of only smashing ridge tillage，among which the effect of applying biochar with 22．5 t /hm2 application amount is the best．

In order to explore the hydraulic characteristics of branch and capillary jet three-way combination, four irrigation districts are composed of branch Jet Tee, common branch three-way, capillary Jet Tee and common capillary three-way. The hydraulic properties of different total inlet pressure (9.5 m, 12 m, 14 m, 15.5 m head) and different drip irrigation belt length (60 m, 70 m, 80 m) are studied. The results showed that the average flow rate of drip irrigator connected with jet tee is less than that of common tee when the total inlet pressure is the same; when the inlet pressure and the length of drip irrigation belt are the same, the irrigation uniformity of No.1 irrigation district is the highest, and that of No.4 irrigation district is the lowest, and the irrigation uniformity coefficient of No.1 irrigation district is 2.56%-3.32% higher than that of No.4 irrigation district, and the flow deviation rate is reduced by 5.0%. 6%-8.20%. When the length of drip irrigation belt is the same, the uniformity coefficient of irrigation in four irrigation districts increases with the increase of pressure head. When the inlet pressure is the same, the uniformity coefficient of irrigation decreases with the increase of drip irrigation belt length. The research results provide a theoretical basis for the development and application of new irrigation district.

In view of the shortage of water measuring facilities in U－shaped channels with steep bottom slope，it is proposed to use the water－fall in U－shaped channels as water measuring buildings． Based on the theoretical analysis of the relationship between critical water depth，hc，in the upstream of water－fall and flow rate in U－shaped channels，in this paper，the water depth of each section in the upstream of water－fall was measured through prototype tests of hydraulic performance of water－fall with 4 types of bottom slopes and 6 types of flow rate，and the change trend of water surface line under different bottom slopes and flow rates was analyzed． The results show that when the bottom slope is constant，the water depth of the upstream sections increases with the increase of the discharge; there is a good correlation between end－depth and critical depth hc of water－fall of U－Shaped Channel． Two kinds of relationships between he and hc were established． The calculated discharge value was very close to the measured value，and the error was less than 10%．

In order to increase the output and water use efficiency of alfalfa，the experiment was conducted to study the effects of regulated deficit irrigation ( ＲDI) on plant heights，chlorophyll content，stem and leaf ratio and hay yield of alfalfa under subsurface drip irrigation． Three lower irrigation limit treatments are set in the experiment． 70% of the field water holding capacity is the control treatment，and two regulated deficit irrigation treatments are set at 50% and 60% of the field water holding capacity． The results show that the height and grass yield of the first two stubble of alfalfa decrease with the increase of irrigation deficit，but the effect on the third stubble is not significant; regulated deficit irrigation has no significant effect on the SPAD value and stem－leaf ratio of alfalfa; hay yield of alfalfa does not decrease significantly under light regulated deficit irrigation ( 60% of field water capacity) ．The comprehensive analysis shows that low regulated deficit irrigation with subsurface drip irrigation ( 60% of field water holding capacity) can achieve high yield and water saving production of alfalfa．

In order to more accurately predict the reference crop evapotranspiration，the data was nonlinearly regressed using the BP neural network． Weights and thresholds in BP neural network algorithms were optimized by Mind Evolutionary Algorithm． Finally，a reference crop evapotranspiration prediction model ( MEA－BP) based on BP Neural Network optimized by Mind Evolutionary Algorithm was established． The results show that the maximum commensurate error of the optimized BP neural network decreases from 13% to 7．2%，and the average relative error decreases from 6．8% to 3．4%． The prediction effect of the model was explored in the absence of meteorological data． When the number of model input parameters was four，the average absolute error was about 0．2 mm ( the predicted value was about 3～ 6 mm) ，and the effective coefficient and correlation coefficient of the model were basically above 0．9． When the number of model input parameters is three， the average absolute error is about 0．25 mm，and the effective coefficient and correlation coefficient of the model are basically above 0．8． It can be found that when the number of input parameters is 3 or more，and the significant influence factor of the effective light duration is included simultaneously，the overall calculation accuracy of the model and the overall practicality are good，which can provide a reference for the prediction of crop irrigation water amount．

This paper takes winter wheat as the research object in Yangling District, obtained the pictures of the study area by using six wing unmanned aerial vehicle equipment with ADC Lite, A total of 65 samples were selected, each with a sample area of 1 × 1 m. The average chlorophyll value of 7 leaves of different plant canopies was measured as the measured chlorophyll value of the sample with UAV synchronization，And GPS recording . The acquired multispectral images were spliced using Pix4D mapper software. 8 spectral parameters was used to acquire the multispectral images. Correlation coefficients were above 0.67, such as SAVI、EVI2、DVI、RVI 、NDVI、EVI and ARVI which were used to establish the regression model aiming to predict the SPAD value of wheat leaf. The inversion model was constructed by one-dimensional linear regression and multiple linear regression and comparative analysis. The results showed that the SAVI-SPAD model had highest precision（R2 were 0.866 and RMSE were 0.245）. The research result can be used as a technical means for SPAD remote sensing monitoring of wheat leaves.

In order to develop a new Venturi fertilizer，improve its ability to absorb fertilizer and adapt it to different conditions of inlet and outlet pressure differential，the optimal structure combination scheme of contraction and diffusion section is discussed under the same ratio of inlet and outlet diameters． In this paper，the solidworks 2016 and CFD software were adopted to model and calculate 14 different models． The four indexes，including fertilizer absorption amount，fertilizer－liquid ratio δ，fertilizer concentration γ and fertilizer efficiency η，and other indexes，including flow field pressure，velocity，turbulent kinetic energy and the streamline distribution，of different structure combination forms are studied to comprehensively evaluate the fertilizer absorption performance． The results show that: ① there is a power function relationship between the pressure difference and the amount of fertilizer absorption． The larger the pressure difference is，the larger the amount of fertilizer absorption is，but the trend of increase is slower and slower． ② compared with the same series of products，the structural scheme of bell－bottom contraction section and streamlined diffusion section shows that the maximum fertilizer absorption is increased by 80%，the concentration of fertilizer liquid changes most stable with the pressure difference，and it has the strongest adaptability to different working conditions． ③ under the same working conditions，the structural scheme of bell inlet contraction section and streamlined diffusion section generates the maximum vacuum，minimum pressure and maximum velocity near the throat，and the average turbulent kinetic energy on the central section corresponding to the vortex zone is the minimum，which is most conducive to fertilizer absorption． Based on the analysis of fertilizer absorption performance and flow field，it can be found that the optimal combination is bell － bottom contraction section and streamline diffusion section．

To examine the demand of water at different growth stages of plastic tunnel eggplant ,the negative pressure irrigation facilities were applied to irrigate eggplant at different growth stages seedling period(blooming and fruit period, and harvest period)using different water supply tension (5kPa,10kPa,15kPa,20kPa,25kPa) to research the effect of different water supply suction on growth, yield and water use efficiency of eggplant.The results showed that the soil water content decreased with the increase of water supply tension. When the water supply tension is 5~25kPa, the relative water content of the soil varies from 49% to 97%. There was a linear relationship between plant height and different water supply tension. Different soil moisture treatment at seedling period has the highest coefficient of determination for height of eggplant, and R2 was 0.8958. The eggplant stem diameter has three linear relationships with different water supply tension. Different soil moisture treatment at seedling period has the highest coefficient of determination for stem diameter of eggplant, and R2 was 0.9947; Yield and WUE had a parabola change tendency under five treatments at each growth stage; The maximum yield and WUE appeared in seedling period blooming and fruit period, and harvest period is15kPa, 15kPa, 10kPa. The results will enrich water regulation theory in precision irrigation of vegetables in plastic tunnel.

In China, groundwater pollution is becoming more and more serious, and groundwater vulnerability assessment is an important means to protect groundwater resources. Based on the aquifer vulnerability index (AVI) and electrical resistivity survey, a new groundwater vulnerability assessment method is established. The method acquires the apparent resistivity data through one-dimensional and two-dimensional electrical resistivity exploration, and obtains the thickness and resistivity value of the vadose zone by inversion calculation. Then the integrated electrical conductivity (IEC) could be calculated according to the established quantitative model. The integrated electrical conductivity is a reflection of the overall characteristics of the vadose zone and can describe the vulnerability of the groundwater system more accurately in the study area. The case study shows that the method is a low-cost, non-invasive, high-precision groundwater vulnerability assessment method which can reflect groundwater vulnerability objectively. Thus, the proposed method is an efficient tool to prevent groundwater pollution and protect the ecological environment.

With the steady increase of population and rapid development of industry and agriculture, the water environmental capacity of the Jushui River is becoming an important factor restricting the development of cities and towns in the basin. Based on the hydrological and water quality data, the water environmental capacity of the Jushui River was calculated in sections. Based on MIKE21, two dimensional hydrodynamic (HD) and convection-diffusion (AD) models were established, the trend map of water quality variation in the middle and lower reaches of the Jushui River was obtained by simulation, besides the water environmental capacity of the main pollutants were analysed. In general, most river reaches have limited capacity to absorb pollution. In order to achieve the goal of controlling the total amount of pollutants entering the river, it is needed to strengthen pollution prevention and control from the aspects of urban and rural domestic sewage treatment, agricultural non-point source controlling, and water quality monitoring at boundary sections, so as to realize the sustainable development of water resources.

In order to study the development status of water resources carrying capacity of Ningxia，the Ningxia＇s overall and Northern Yellow Ｒiver Irrigation Zone，the central arid zone and the Southern Mountainous Area were taken as study object，the dynamic changes of water resources carrying capacity，driving factors and development in the future ( 2020，2025，2030) in different situations were analyzed by using principal component analysis，fuzzy analytic hierarchy analysis，GM( 1，1) and different scenario models． The results showed that the change trend of the northern Yellow Ｒiver irrigation area was similar to that in Ningxia，which showed a steady increase trend from 2004 to 2016; although the central arid zone was also on the rise，the change range was not big; the fluctuation of southern mountainous area was larger， although it also showed a certain increase，the effect was very small; the benign development of water resource carrying capacity was at the cost of sacrificing part of ecological environment; the order of driving effects of different factors was forest coverage rate ＞ ecological water use rate ＞ agricultural dependence rate ＞ annual precipitation ＞ per capita GDP＞ Engel coefficient． In the future，the carrying capacity of water resources in Ningxia region under the four scenarios is well developed，ranking as scenario 3＞，current situation ＞scenario 2＞scenario 1．

In this paper，the water resources in main stream of Hanjiang Ｒiver was taken as the research object． Firstly，the water footprints of 10 cities around main stream of Hangjiang Ｒiver from 2008 to 2015 were calculated to realize the spatial－temporal features analysis of the water footprint parameters． Then，based on PSＲ theory，a comprehensive index system，including water footprint indexes and regular indicators，was constructed for the sustainable utilization of water resources． Afterwards，the entropy weight method and grey target model were used to evaluate the spatial difference of sustainable utilization level of water resources in main stream of Hanjiang Ｒiver in 2015． The results showed as follows: ① the total water footprint was slowly increasing during 2008 to 2015 with the increase rate of 24．28×108 m3 per year，and water footprint of agricultural production played the dominant percentage in the total water footprint，averagely accounting for 87．78%． ② The largest economic benefits per unit water footprint was in Wuhan with 62．72 yuan /m3 ，while the values were concentrated between 9 and 22．72 yuan /m3 in the all remaining cities． And the weakest pressure index of water resource was in Hanzhong，Ankang and Shiyan，while the values exceeded 2 in the remaining cities． ③ In 2015，the sustainable utilization of water resources was dominated by the middle and poor grades in middle and lower reaches of main stream of Hanjiang Ｒiver，and only Hanzhong and Ankang in upstream reached good level． Similarly，standard layers also presented better level in upstream than in middle and lower reaches for sustainable utilization level of water resources．

Groundwater quality assessment is an important issue in environmental protection． Based on Directed－Hasse Diagram Technique ( D－HDT) ，this study conducted the modeling，interpretation and evaluation of groundwater quality in accordance with national standards． This method solves the problem of weighting in the traditional method of water quality evaluation． In this way，the weight value of each evaluation index is not directly involved in the calculation process，and evaluation can be completed only by ranking the weight of each index． However，D－HDT can only reflect the quality ranking among samples and the quality level cannot be determined． Therefore，in this paper， together with the samples to be evaluated，five sets of standard grade samples are constructed according to the Groundwater Quality Standard ( GB/T 14848－2017) to participate in the evaluation． This study shows that based on the objective criteria，assessment results under D－HDT are intuitive and objective，and further research and application of D－HDT can be foreseen．

Based on the MOD16 data of global evapotranspiration products，the Heihe Ｒiver Basin was used as the research object． Through the trend analysis method，the interannual and intra －annual spatial and temporal variations of the actual evapotranspiration ( AET) and potential evapotranspiration ( PET) on the surface of the Heihe Ｒiver Basin from 2001 to 2017 were studied． The results show that: ① The average annual AET and PET of the Heihe Ｒiver Basin have obvious spatial distribution characteristics． The spatial average range of the average AET value is 79．88～ 509．22 mm，and the spatial value range of the average annual PET value is 338．55～ 1 876．75 mm． ②This study analyzes different land use types． For the multi－year average AET，the forest land is the largest，followed by grassland，cultivated land，and urban land，and the unused land is the smallest; for the multi－year average PET，the unused land is the largest，followed by the town Land， cultivated land，grassland，and forest land are the smallest． ③ On the annual scale，the interannual fluctuations of AET and PET in the Heihe Ｒiver Basin have not changed much． The AET fluctuation range is 222．08～ 352．11 mm，the average annual AET value is 292．01 mm， the PET fluctuation range is 1 084． 61 ～ 1 206． 69 mm，and the average annual PET value is 1 146． 56 mm． On the monthly scale，the distribution of AET and PET in the Heihe Ｒiver Basin is increasing first and then decreasing． The peak value is in July，and the difference between AET and PET in May，June and July is on a seasonal scale，summer is the season with the largest difference between AET and PET， followed by spring，which proves that the basin is the most arid and water－deficient in summer，with the characteristics of spring drought．

Precipitation is the decisive factor for regional water resources． Precise evaluation of precipitation is of great significance for the rational development and utilization of regional water resources． In this study，the Chongli Area of Zhangjiakou City in Hebei Province was selected as the study area． Considering the changes of topography and geomorphology in the area，the altitude effect of precipitation at different precipitation monitoring points was analyzed importantly，and the infiltration recharge of regional precipitation was calculated． The calculation of the altitude effect of precipitation in Chongli Area shows that: with the increasing of ground elevation，the precipitation shows a significantly increasing trend，and the elevation gradient is 21．3 mm/100 m; according to the altitude effect of precipitation，the infiltration recharge of regional precipitation can be calculated to be 6 302．20×104 m3 and the precipitation infiltration coefficient is 0．056． It can be seen that the precise judgment of the precipitation altitude effect has a significant impact on the calculation of regional water resources．

The evaluation of water－saving level is of great significance for achieving sustainable use of water resources． Based on the water usage data of 31 provinces ( excluding Hong Kong，Macao and Taiwan) ，this paper selected 9 indexes，which are representative and easily accessible，from the four aspects of integration，life，production and ecology，used the analytic hierarchy process and the entropy weight method to jointly determine the comprehensive weight of the evaluation index，divided the water saving－level into 5 levels and used cluster analysis to determine the water－saving level of each province． The results show that: 17 provinces ( autonomous regions and municipalities) are at the initial and primary level，11 provinces ( autonomous regions and municipalities) are at the medium level，and 3 provinces ( autonomous regions and municipalities) are at the excellent level． In terms of space，it presents the pattern that the Beijing－Tianjin－Hebei region is the center and gradually decreases outwards． The water saving level in the north is better than that in the south，and that in the east is better than that in the west．

The effect of irrigation on yield and water use efficiency (WUE) of winter wheat is generally a fixed-point plot experiment. The results are limited by space and time difference and precipitation. It is difficult to reflect the general law of the effect of irrigation on yield and WUE of winter wheat in different regions and different rainfall levels. In this study, winter wheat was taken as the research object, and the published field experimental data were retrieved and integrated. Based on Meta-analysis method, the effects of irrigation on winter wheat yield and WUE in Northwest China were studied quantitatively. The results showed that the yield of winter wheat under irrigation increased by 27.9% (95% confidence interval 23.1%~ 32.8%) and WUE increased by 6.1% (confidence interval 0.1% ~ 12.7%) compared with that of dry farming in Northwest China. With the increase of irrigation volumes, the cumulative average yield increase of irrigation is up to 32.1%, while the relative change rate of WUE decreases to 4.1%. Subgroup analysis of different rainfall years showed that the yield of winter wheat was significantly increased under irrigation conditions. Irrigation in wet and dry years could improve the WUE of winter wheat, but irrigation in normal years could reduce the WUE of winter wheat. The results can provide reference for the scientific formulation of irrigation schemes for winter wheat? in different rainfall years in Northwest China.

In order to better manage the water supply and distribution in the irrigation area and improve the accuracy of water measurement, the flow measurement characteristics of swing-rod open channel measuring device in D50 U-shaped-channel were studied by numerical simulation. Based on computational fluid dynamics, using FLUENT software, VOF method, Realizable k-ε turbulence model and dynamic mesh technology, the flow measurement characteristics of three kinds of swing rods with different materials are numerically simulated. The post-processing software was used to analyze the simulation results, and it was found that the water level of the simulated channel increased with the increase of the flow, and the maximum flow velocity was located below the water surface, which conforms to the basic principle of open channel hydraulics. It is feasible to simulate the swing characteristics of the swing rod with the dynamic mesh technology. The average relative error between flow rate and actual flow rate calculated by the formula is less than 3%, which can satisfy the accuracy requirement of open channel flow measurement.

There are some problems of traditional citrus irrigation methods in mountainous areas. Such as low efficiency, unscientific, low utilization rate of water resources, and so on. This paper designs a mountain citrus intelligent irrigation expert system based on internet of things and artificial intelligence. The sensors of each node monitor soil moisture and other related information, and upload to the server via wireless sensor networks and GPRS. Based on the collected environmental data, the expert system combines expert knowledge with the weather forecast rainfall information obtained by the network interface, and makes control adjustments after comprehensive trade-offs. The expert system also trains the semantic model through artificial intelligence natural language processing technology to realize automatic question and answer, and guide the user to cultivate the function of citrus. The experimental results show that the system can monitor the orchard environment in real time, control the soil moisture in a suitable range according to the water demand and natural rainfall in different periods of the crop, and has the characteristics of good stability, energy self-sufficiency, and high intelligence.