Turf evapotranspiration， resulting from turf expansion and excessive irrigation， is the primary aspect with respect to the consumption of urban water resources in northern China. Moreover， water shortage has become a threat to local economic development and ecological security. Understanding the mechanism of turf evapotranspiration contributes to sustainable utilization of urban water resources and establishment of water-saving society. Taking the typical turf (Poa Pratensis) in Zhangjiakou City of Hebei Province as the study object， the dynamic variations of turf evapotranspiration and impacting factors were analyzed at month-， day- and hour-scale based on the data from weighing lysimeter and principal component analysis. The results indicated that：①Turf evapotranspiration showed the highest (lowest) value in summer (winter) during the year， with the average peak value 5.27 (0.29) mm/d in June (February). ② The hourly evapotranspiration changes in a typical day exhibited a single-peak state， where low evapotranspiration occurred in the morning and evening but high evapotranspiration occurred in the noon at a day-scale. Specifically， turf evapotranspiration was significantly affected by solar radiation and air temperature. ③At the depths of 10 cm and 20 cm， the dynamics of turf evapotranspiration were highly consistent with that of soil moisture. ④Established principal component regression model greatly simulated (R² =0.70,p＜0.01) the relationship between turf evapotranspiration and affecting factors， and the degrees of correlation were as follows： photosynthetic effective radiation > air temperature > soil water content at 10 cm > air humidity > wind speed > soil water content at 20 cm > soil water content 30 cm. This study revealed the change in turf evapotranspiration， and provided a scientific basis for the establishment of urban water-saving society in Zhangjiakou City.

In order to deeply explore the spatial transpiration characteristics of citrus canopy and its corresponding relationship with stem fluid flow， the five-point temperature measurement method was adopted， and the infrared images of citrus canopy in five directions were taken by thermal imager to obtain the canopy temperature and reference canopy temperature. The three-temperature model was used to compare the estimated leaf transpiration rate of the model with the measured stem flow rate and the transpiration changes of citrus canopy in different directions were studied. The results showed that the diurnal variation curves of stem velocity rate and the canopy leaf transpiration rate of citrus were different， and the determination coefficient (R²) was 0.14. On the whole， the diurnal variation laws of canopy temperature and air temperature in different directions were similar. The average transpiration rate of Citrus in different directions were as follows： East > West > North > South > top. The above results show that： (1) there is a time lag effect between canopy transpiration and stem sap flow， and the leaf transpiration rate estimated by the three-temperature model can not reflect the change characteristics of trunk sap flow in real time. (2) The higher the temperature， the more significant the difference of canopy temperature in different directions. (3) The spatial transpiration of citrus canopy has obvious spatial differences， which reveals the spatial variation law of citrus canopy transpiration rate.

In order to improve the economic benefits of irrigation district and further improve the agricultural water rights system， the study on the agricultural water rights allocation of the irrigation district was conducted. In view of the differences of foundation condition and planting structure of different branch canals in irrigation district， combined with the actual situation of engineering condition， society， economy and ecology in irrigation district， a method of agricultural water rights allocation among branch canals in the irrigation district was proposed to optimize economic benefits under the constraints of the current situation of the irrigation district. The improved analytic hierarchy process and fuzzy comprehensive evaluation methods were adopted to allocate agricultural water rights among branch canals in Heping irrigation district. In this study， the hierarchy was classifified according to 4 categories of second-grade indices， 12 third-grade indices and 17 fourth-grade indices， and the Matlab software was used for data processing. The results showed that the water rights allocation amounts of 1，3，5，6，7，8，9，12，15 and 16 branch canals by the model were larger than the water rights allocation amounts by area， with a variation range of -0.09% to -9.90%. The water rights allocation amount of 2，4，10，11，13 and 14 branch canals by model were less than the water rights allocation amount by area， with a variation range of 0.97% to 8.62%. There was a certain deviation between the allocation results of agricultural water rights model in irrigated district and the existing water allocation results by area， ranging from -9.90% to 8.62%. The results of the model allocation had significant advantages in economic benefits. The improved analytic hierarchy process and fuzzy comprehensive evaluation method proposed in this paper has strong operability， good rationality and fully follows the characteristics of studying the current situation of irrigation districts.

With the intensification of global climate change and human activities， the risk of flood disaster at flat irrigation district is increasing continuously. In this paper， an evaluation method of waterlogging loss rate of rice was proposed based on the waterlogging process. On the basis of the function relationship between the flooded depth and the flooded duration and the rice waterlogging yield reduction rate， this method can calculate the daily cumulative rice waterlogging yield reduction rate under the condition of daily water depth change by a set of calculation processes of interpolation and incremental superposition， and then obtain the cumulative process of the rice waterlogging yield reduction rate under the process of flooded depth change. The root mean square error between the yield loss calculated by the yield reduction rate function and the experimental observation value is less than 15%， the correlation coefficient is greater than 0.84， and the simulation efficiency of the model is more than 0.71. This method can be applied to the calculation and evaluation of waterlogging loss in the rice growing area， which provides a scientific calculation method for the post-disaster recovery and pre-prediction in the rice growing area.

The purposes of this study were to determine the differences of the effects of fly ash and earthworm manure on soil evaporation， and to explore the appropriate application mode and dosage. Three mulching treatments (mulching thickness of 1， 2.5 and 4 cm， respectively) and four mixing treatments (application rate of 10%， 20%， 30% and 40%， respectively) were designed with the greenhouse soil as the control. Soil evaporation was continuously measured for 16 days. Combined with soil organic matter content， hydro-physical properties and the characteristics of fly ash and earthworm manure， the reasons for different effects on soil evaporation between fly ash and earthworm manure application were further analyzed. The results showed that compared with the control， the cumulative evaporation decreased by 30%~34% and 17%~48% for the soil with fly ash and earthworm manure mulching application， respectively； the cumulative evaporation decreased by 0%~6% and 4%~14% for the soil with fly ash and earthworm manure mixing application， respectively. Fly ash had better effect of inhibiting evaporation than earthworm manure when the covering thickness was 1 cm.However,earthworm manure had better effect of inhibiting evaporation than fly ash when the covering thickness was 4 cm. Both mulching and mixing application of the two substances could lead to the increase in the content of organic matter， which was the main reason for inhibiting soil evaporation. The two substances had different inhibition effects on evaporation， which were caused by different organic matter content， color and particle composition between them. In addition， the water content of the soil with fly ash and earthworm manure mulching and mixing application were higher than the control. The porosity and water holding capacity of the soil with earthworm manure mixing application were higher than the control. In conclusion， from the perspective of inhibiting soil evaporation and maintaining soil moisture， fly ash had better effects than earthworm manure under mulching application of the thin layer. However， earthworm manure had better effects than fly ash under the mulching application of the medium and thick layer and with the mixing application.

In order to improve the quality and taste of tomato and meet the market demand of consumers， the yield， nutritional quality and taste of three taste tomato varieties were measured in a field plot experiment. The results showed that： under different water control conditions， different varieties had different responses. The yield of “Gaotang 200” was significantly reduced under water-controlled irrigation， and the yield was reduced by 24.22% and 28.07% under the irrigation treatments of 60% W and 40% W， respectively. Water-controlled irrigation increased soluble solid content， Vc content， soluble sugar， sugar acid ratio and sensory evaluation of tomato “Gaotang 200” and “Kg1606”， and improved nutritional quality and taste obviously. Sugar and acid ratio had a significant positive correlation with the sensory evaluation of tomato fruit. In general， when irrigated with 40% W， among the three varieties， “Kg1606” had a yield reduction of 15.17%， which was the least. Its sugar and acid ratio was high， its taste evaluation was significantly better than the other treatments. So it is suitable for water-saving high quality tomato cultivation.

In order to explore the influence of different drip irrigation methods on the change of soil profile salinity in coastal saline-alkali soil， a field experiment was conducted with taking Tianjin coastal saline-alkali soil as the research object. Two treatments， conventional drip irrigation (CI) and drip irrigation under mulch (FI) were designed and the changes of Mg²⁺， Na⁺， K⁺， SAR and K⁺/Na⁺ in soil profile under different drip irrigation methods were studied. The results showed that the concentrations of Ca²⁺， Mg²⁺ and Na⁺ in 0~60 cm soil layer under CI and FI treatments were significantly decreased after irrigation. After rainfall， the concentration of Na⁺ and SAR in 0~20 cm soil layer and the concentration of Mg²⁺ in 20~60 cm soil layer were significantly decreased under CI treatment. In the process of water redistribution， the concentration of Ca²⁺， Mg²⁺ and Na⁺ in the 0~20 cm soil layer showed the trend of CI treatment higher than FI treatment， while K⁺/Na⁺ showed the trend of CI treatment lower than FI treatment. After irrigation， soil total salt in 0~20 cm soil layer decreased by 25.2% and 32.6% in CI and FI treatments， while Na⁺ concentration decreased by 37.3% and 57.7% in 0~20 cm soil layer， respectively. After rainfall， the soil total salt in 0~60 cm soil layer under CI treatment decreased by about 30%， while the soil Na⁺ concentration decreased by more than 50%. For coastal saline-alkali land， under CI and FI treatments， soil total salt had significant positive correlation with soil Na⁺ concentration and significant negative correlation with soil K⁺ concentration. So it is more accurate to evaluate the effect of irrigation and rainfall on crop rhizosphere salinity by using soil Na⁺ as an index.

Soil moisture plays an important role in the hydrological process and vegetation restoration in arid and semi-arid regions. Exploring the temporal stability characteristics of soil moisture in the fixed dunes of the Mu Us Sandy Land is of great significance to the regulation of water resources and the improvement of the ecological environment in this area. The windward， leeward and slope tops of fixed dunes on the southeastern edge of the Mu Us Sandy Land were selected for grid layout. The surface (0~5 cm) soil water content was measured by soil temperature and humidity recorder (TMS) from July to October 2019. Then， the spatial variability and temporal stability characteristics of the surface soil water was analyzed. The results showed that during the study period the average surface soil water content was 21.00%. Temporal and spatial changes were generally characterized by moderate variability. The spatial model of surface soil water content had weak similarity in observation time， and each date pair had a low correlation coefficient. The average relative difference (MRD) of soil water content was between -17.24% and 18.80%， and the average relative difference standard deviation (SDRD) and time stability index (ITS) were 12.70% and 14.20%， respectively. The surface soil water content had good time stability. The observation points with higher soil water content had lower SDRD and ITS， and the time stability of observation points with higher soil water content was better than that of observation points with lower soil water content. Based on the analysis of the time stability characteristics of soil water content， the 77^th observation point could better represent the average level of surface soil water content in the study area (coefficient of determination was 0.876 9).

In order to meet the serious challenge between agricultural water shortage under changing environment， determining appropriate canal and well irrigation water usage ratio in canal-well combined irrigation district is an important issue for the sustainable and secure utilization of groundwater development. In this study， a semi-structured interview was first used to conduct a large number of field surveys in Baojixia irrigation District in Shaanxi Province to collect basic data， such as crop planting types， crop yield， agricultural cost， irrigation water source selection and irrigation water consumption. The observed data of farmers’ irrigation behavior was conceptualized and programmed by using Python language to develop a social hydrological model， in which the irrigation water usage behavior was coupled with the hydrological process in the crop root zone to simulate the effects of canal and well irrigation water usage ratios on groundwater level dynamics， crop yield， and farmer livelihoods. The Nash efficiency coefficient of the model is 0.58， which indicates that the model can simulate the groundwater level in the combined canal-well combined irrigation district. The results are as follows. In order to maintain a stable groundwater level， the canal and well irrigation water usage ratio should be 2∶98， 28∶72 and 30∶70 for wet， normal and dry years respectively in the upper part of Baojixia irrigation district. For the lower part of the irrigation district， it should be all-well irrigation (0)， 28∶72 and 29∶71 for wet， normal and dry years. In another case， groundwater level can rise by 2 meters when the canal and well irrigation water usage ratio is 10∶90 and 17∶83 for the upper part and the lower part of the irrigation district， respectively， in wet year. Groundwater level can decrease 2 meters when the canal and well irrigation water usage ratio is 21∶79 and 13∶87 in the upper part and lower part， respectively， in the dry year. Different ratios will not change the crop yield， however， the average net income per hectare decreased slightly because of different groundwater level depth， which affects the energy consumption for groundwater abstraction. The model developed in this paper can be adopted to simulate the impacts of irrigation on groundwater level， crop yield and farmers’ livelihoods in canal-well combined irrigation district， which has a good potential in terms of providing strong technical support for the sustainable and secure utilization of groundwater development in irrigation district.

In order to clarify the influence of air filling on the clogging of the dripper， the flow changes and clogging laws of the embedded patch dripper with four different flow channel structure parameters were studied， and the main parameters affecting the clogging of the dripper were analyzed. The results showed that： under aerated irrigation， the capillary sediments of the E1~E4 drippers increased by 36%~74.65%， the flow channel sediments of the E1~E3 drippers increased by 10.94%~88.71% and that of E4 decreased by 162.2% compared with that without aerated. Aerated irrigation significantly affected the clogging of the dripper（P<0.05）. Under aerated irrigation， the rated flow rate， inlet fence area， channel length and channel structure type had significant influence on the dropper blockage. The inlet fence area had the greatest influence on the dripper blockage. E4 with the largest inlet fence area had the lowest degree of blockage， while E1， E2 and E3 with the smaller inlet fence area had a relatively high degree of blockage. Compared with the non-aerated treatment， the relative flow rate of E1~E3 at the end of irrigation decreased by 20.83%~26.11%， and the relative flow rate of E4 increased by 30.91%. The influence of inlet fence area on dripper blockage of aerated drip irrigation was higher. For aerated irrigation， the dripper with a large area of inlet fence should be selected， and the dripper should be arranged on the top of the capillary tube to avoid silting and blockage in the capillary tube.

In this study， the salt drainage effects of shallow ditch on different types of soil were comparatively studied by field and laboratory experiments and numerical simulation. Based on soil particle analysis， water movement parameters and soil salt dispersion coefficient， a numerical model was established to study the soil water and salt movement during the growth period of cotton field under drip irrigation with salt drainage shallow ditches. The model was used to compare the distribution of soil water and salt of two different groups of soil under the condition of salt drainage shallow ditches， and to analyze the influence of soil type on the distribution of soil water and salt of cotton field under mulched drip irrigation. The results showed that the water holding effect of silty loam was better than that of loam. Compared with loam， salt drainage shallow ditches have better salt-removal effect in silt loam， and the salt is mainly concentrated on the slope of salt drainage shallow ditches.

In order to achieve the dual goals of saving agricultural water resources and guaranteeing food security， this study provided an optimized strategy for agricultural water price reform. Based on the survey data of farmers in four typical wheat producing areas in Hebei Province in 2020， the standard Penman formula was used to calculate the water-saving space for normal growth of wheat， and then the agricultural water price that just meets the water requirement for normal growth of wheat was calculated based on the price elasticity of agricultural irrigation water demand， and the adjustment space of agricultural water price was discussed from the perspective of food security. The results show that for wheat production， the current agricultural water price can gradually increase to 0.546 yuan/m³， and the space of water price increase is different in different regions due to the difference of resource endowment. Wheat planting cost per unit area and application cost of water-saving technology are significantly positively correlated with agricultural irrigation water consumption. It is suggested that the pricing of agricultural water should be based on local conditions， and factors such as regional environmental differences， crop species differences and resource endowment differences should be fully considered. When the agricultural water price is moderately raised， the policies of water-saving incentive and water subsidy should be implemented to guarantee farmers' income and grain production.

In order to study the effect of different irrigation flow rate on the wetting body of bubbled irrigation and bubbled-root irrigation under the same irrigation amount， the indoor soil water infiltration experiment and theoretical analysis were carried out. The results show that the wetting body shape of bubbled irrigation is an approximate hemispherical body， and the wetting body shape of bubbled-root irrigation is an approximate half elliptical sphere after infiltration. The flow rate of emitter has a significant effect on the shape of wetting body of bubbled irrigation. The larger the flow rate is， the flatter the shape of wetting body is. However， within a certain range of flow rate， the flow rate of emitter has no significant effect on the shape of wetting body of bubbled-root irrigation. Under the same irrigation amount and flow rate， the infiltration distance of bubbled irrigation in the horizontal direction is significantly larger than that of bubbled-root irrigation， and the infiltration distance in the vertical direction is significantly smaller than that of bubbled-root irrigation. Compared with bubbled irrigation， bubbled-root irrigation is not easy to produce soil surface water accumulation， water distribution is deeper， the amount of infiltration water is easier to reach the root zone of crops， which reduces the ineffective evaporation of water and is benefit to the attraction of crops to soil moisture.

In order to explore the effect of straw mulching amount on water-saving effect of summer maize under ridge and furrow irrigation， four straw mulching amounts (M0：0， M1：1 500 kg/hm²， M2：4 500 kg/hm²， M3：7 500 kg/hm²) and four lower limits of water control (I1：55% FC， I2：60% FC， I3： 70%FC and I4：80% FC) were used to study the effects of ridge and furrow irrigation on the growth， water use efficiency and yield of summer maize under different straw mulching amount and lower limit of water control. The results showed that the height of summer maize under different treatments increased firstly and then decreased with the increase of lower limit of water control. Under the same lower limit of water control， straw mulching at 4 500 kg/hm² and 7 500 kg/hm² could significantly increase the height of summer maize. When the lower limit of water control was 60% FC to 80% FC， the leaf area of summer maize reached the maximum when the straw mulching amount was 4 500 kg/km²， and the leaf area had the most significant promoting effect. In a certain lower limit of water content， the more straw mulching amount， the more beneficial to increase the dry matter accumulation of summer maize. The dry matter accumulation of summer maize increased with the lower limit of water control at the same straw mulching amount. From 55% FC to 60% FC， 70% FC and 80% FC， the average increase of water consumption during the whole growth period of summer maize was 5.06%， 11.45% and 23.48%， respectively. The effects of water， straw mulching and their coupling treatments on yield， WUE and PUE of summer maize reached extremely significant levels (p< 0.01). When the lower limit of water control was 70% FC and straw mulching amount was 4 500 kg/hm²， the yield of summer maize (6 922.54 kg/hm²)， WUE (2.09 kg/m³) and PUE (5.48 kg/m³) were the highest. And I3M3 was the best treatment.

In order to reveal the nitrogen utilization and absorption of summer maize under different water and fertilizer treatments， the ¹⁵N tracer technique was used in the experiments， in which four levels of nitrogen application at 0 kg/hm² (CK)， 120 kg/hm² (N1)， 180 kg/hm² (N2)， and 270 kg/hm² (N3)， and two levels of irrigation at 132 mm (I1) and 166 mm (I2) were set. The absorption and distribution of fertilizer nitrogen and soil nitrogen by different mature maize organs during their mature stage under different levels of irrigation and fertilization were studied and the excitation law of fertilizer nitrogen to soil nitrogen and the residue and loss of fertilizer nitrogen in soil under different treatments were analyzed. The results showed that the nitrogen absorbed by maize from fertilizer accounted for 19.43%~28.62% and the nitrogen absorbed by maize from soil accounted for 71.38%~80.57% under different irrigation and fertilization conditions. The competition ability of maize organs to fertilizer nitrogen from large to small was represented by grain， stem and leaf. All soil nitrogen excitation effects were positive， and the excitation rates ranged from 119.16% to 169.19%. The fertilizer nitrogen absorption rate， soil residual rate and loss rate of summer maize after harvest were 29.41%~50.75%， 20.45%~31.41% and 24.67%~41.26%， respectively. Among all treatments， the fertilizer nitrogen absorption rate of summer maize under N2I2 treatment was the highest (50.75%). The agronomic use efficiency of nitrogen and water use efficiency of summer maize ranged from 1.63 to 7.72 kg/kg and 1.09 to 1.30 kg/m³. The proper ratio of water and fertilizer is beneficial to make full use of nitrogen fertilizer， save water resources and reduce waste.

To calculate reference crop evapotransportation(ET ₀) with limited data and obtain the most accurate HS model in the hilly area of central Sichuan Basin， this paper has divide the hilly area of central Sichuan Basin into the north area(Ⅰ)，central area(Ⅱ) ，south area(Ⅲ).Then， ET ₀ in 5-day-scale， monthly-scale and years-scale were calculated by HS model(HS)， Jalal HS(HS-1) ，Samani HS(HS-2)， Qingfang Hu HS (HS-3)， Yonghong Yang HS(HS-4)， Chen Li HS(HS-5) and Yue Jia HS(HS-6)， with the comparation to the ET ₀ calculated by Penman-Monteith model(PM). The results show， HS-5 model is the best one in 5-day-scale with the index of agreement(IA)， relative root mean square error(RMSE)， standard error of estimate(SEE) and relative error(RE) only in 0.94~0.97， 1.89~2.97mm/(5d)， -0.05~0.22 and 1.36~1.93 mm/(5 d) respectively； HS-6 model performs good not only in monthly-scale but in years-scale， since its IA and RE decreased to 0.98~1.00 and -0.10~-0.01 in all areas except Guangyuan(RE is 0.47， IA is 0.79). HS-3 and HS-4 models have a SEE between HS-5 and HS-6 [1.69~2.60 mm/(5d)^{and 1.50~2.70 mm/(5d)] while other parameters lower than them. At the same time， the HS-2 model has a worst performance for it’s lower IA(0.73~0.87，0.71~0.85) and higher RE(0.37~0.69) in 5-day-scale and monthly-scale. Therefore， the HS-5 modified by Chen Li and HS-6 modified by YueJia， so called “Localized HS models”， are regarded as the best HS models in hilly area of central Sichuan Basin to calculate ET ₀ in the absence of data.}