According to the requirements of high flow measurement accuracy and small head loss in the last stage channel below the branch channel, the suitable application conditions of different measuring flumes and flows were sought in this study. The standard \mathit{k} - \mathit{\epsilon } model was used to simulate the flow hydraulic characteristics of the Parshall flume and long-throated flume under different discharge. The simulation accuracy, water surface profile, velocity, streamline and head loss under various flow conditions were analyzed. The results show that:①the simulation accuracy of Parshall flume is better than that of long-throated flume with the errors for both being within 10%. There is high simulation accuracy of Parshall flume with the increase of discharge, while the simulation accuracy for long-throated will decrease with increase of discharge. ②Both the Parshall flume and long-throated flume have backwater effect on the upstream channel. However, water surface fall in the Parshall flume is more gently than that in the long-throated flume, which leads to low water head loss in the Parshall flume. ③Due to the obvious backwater effect of Parshall channel, the velocity in the throat increases greatly, which is the main reason leading to water head loss in Parshall flume. But for the long-throated flume, water head loss is mainly caused by the change of section at bottom of flume. Therefore, under comprehensive consideration, Parshall flume is suitable for low discharge measurement of channel, and long-throated flume is more suitable for high discharge measurement.

In order to explore the complex relationship between potato quality and soil nutrients in root zone, so as to provide scientific basis for precise irrigation and fertilization of potato production in arid area of Northwest China. In this study, 57 different varieties of potatoes often planted in this area were taken as the research object, and the tuber quality and soil nutrients in the root zone were measured respectively. The important soil nutrient factors affecting potato quality were selected by variable importance projection (VIP), and the regression equation model between potato quality and soil nutrient factors was established by partial least squares regression (PLSR). The results showed that the main nutrient factors affecting potato quality in Northwest China were soil conductivity, available potassium, nitrate nitrogen and water content. Soil nitrate nitrogen is the primary soil nutrient factor affecting potato yield and vitamin C. Soil conductivity is the primary soil nutrient factor affecting the activities of potato starch, crude protein and polyphenol oxidase. There was a very significant negative correlation between soil available potassium and potato reducing sugar, and a significant negative correlation with total soluble sugar. Therefore, it is an effective way to improve the quality of potato in Northwest China by regulating soil conductivity and increasing the application of potassium fertilizer and nitrogen fertilizer.

In recent years, crop growth model has been widely used in yield prediction, field management guidance and precision agriculture of various crops. Domestic research on the application of crop growth models is mostly in food crops, while tobacco, as an important economic crop, is still lack of research on growth simulation model. At present, the domestic use of crop models is mainly in scientific research, and there are few that can really guide production. This paper introduced the growth simulation model WOFOST to conduct relevant pioneering research on tobacco growth simulation and irrigation. The historical planting data of tobacco in Xuchang, Henan province were collected. Field experiments were carried out to observe the growth and development of tobacco, and the necessary growth simulation data were obtained. The parameters of the WOFOST model were corrected and verified to complete the calibration of the model parameters and realize the localization of the tobacco model. A variety of irrigation schemes were designed, and local models were used to carry out the simulation. The precipitation in the growing season of tobacco was divided into three types: wet year, normal year and dry year. The simulation results of tobacco irrigation in different types of years were compared and analyzed, focusing on the optimal irrigation amount, time and frequency in dry year. The results showed that the WOFOST tobacco model was a good model for the growth simulation of Xuchang tobacco, and could be used as a sharp tool for tobacco growth research and production guidance. Using the modified model to simulate irrigation, it was found that irrigation benefits were low in wet and normal years. In dry year, irrigation was very necessary. In dry year, if single irrigation was used, the optimal irrigation was 120mm about 10d after bud emergence. The overall effect of two irrigations was better than that of a single irrigation. Irrigation of 120mm was applied 10d-20d before bud emergence and 20d-30d after bud emergence, which could increase the yield the most, but there was a waste of water resources. Considering water saving in a comprehensive way, two irrigations of 60mm each in the same period could obtain higher irrigation contribution rate, which was the optimal irrigation scheme. It was concluded that the application of WOFOST in tobacco growth simulation and irrigation management in China was feasible and worthy of reference and promotion.

In arid and semi-arid areas where rainfall is low and unevenly distributed, it is obvious that ridge and furrow rainwater harvesting planting technology is widely used. Thanks to the joint efforts of many scholars and farmers, the technology has been derived from the original simple ridge-furrow and no-cover technology to various application modes. In this paper, the literature analysis method was used to summarize the development process of ridge and furrow rainwater harvesting from the aspects of structure, mulch material, soil properties, crop yield, water use efficiency and greenhouse gas emissions. The positive and negative effects and development prospects of ridge and furrow rain harvesting technology on production and environment were objectively explained. The results showed that ridge and furrow rainwater harvesting technology could collect rainwater, reduce evaporation area and balance the warming and cooling effects of different mulching materials through micro-topographic changes and mulching methods, so as to regulate soil hydrothermal conditions, fertility and farmland productivity, promote crop growth, and improve water use efficiency and yield. At present, the research of this technology is not only limited to single-season crops in arid and semi-arid areas, but also extended to annual production in double-cropping areas. However, considering the sustainability of the technology in the future, it is believed that the ridge and furrow rainwater harvesting technology combined with environmentally friendly mulching materials and model simulation will be beneficial to alleviate the negative effects of plastic mulching film on the environment and improve the problem that the production is difficult to be mechanized.

In order to make the annual distribution method more reasonable to calculate the ecological discharge of seasonal rivers, the original annual distribution method was improved. Taking the Northwest River, a tributary of the Songhua River, as an example, based on the monthly runoff data of the Northwest River hydrological station from 1956 to 2016, the monthly runoff at 90% guarantee rate was used to replace the monthly minimum runoff, and the period was divided according to the three criteria of season, abundant and dry months, and runoff, so as to calculate the mean ratio of each period under each partition criteria. The ecological flow was calculated by combining the annual average runoff of each month, and the best improved method under the three standards was obtained, which was compared and analyzed with the original annual distribution method, and the results were verified by Tennant method, monthly minimum runoff method and 90% guarantee rate method. The results show that the ecological flow calculated under the three standards is basically consistent with the annual change trend of the ecological flow calculated by the original year distribution method. The overall trend is: improved method 1 (divided by season) > improved method 3 (divided by runoff) > original year distribution method > improved method 2 (divided by wet and dry months). Compared with Tennant method and other hydrology methods (monthly minimum runoff method and 90% guaranteed rate method), the ecological flow calculated by improved method 1 is better than the original annual distribution method. It can not only meet the needs of fish reproduction and survival and river biological growth, but also guarantee the basic ecological function of the river. Therefore, it is reasonable and feasible to improve the intra-year distribution method. In conclusion, using the improved method - the improved annual distribution method to calculate the ecological discharge can better reflect the change characteristics of the river, conform to the calculation of the seasonal river ecological discharge in the north, and be more suitable for the calculation of the northwest river ecological discharge, which can be used as a new idea for the study of river ecological flow.

In order to understand the spatial changes of groundwater quality and its influencing factors in the irrigation area of Kashgar River Basin, descriptive statistical analysis and Piper three-plot diagram method were used to analyze characteristics of groundwater chemical compositions and hydrochemical types. The groundwater quality and irrigation suitability in the irrigation area were evaluated by F score method, USSL diagram and Wilcox diagram method, respectively. The influencing factors of groundwater quality deterioration in the irrigation area were analyzed by factor analysis and ion ratio. The results showed that the order of groundwater quality in irrigation area was as follows: single structure unconfined groundwater > confined groundwater > unconfined groundwater in confined area. According to the evaluation of irrigation suitability, the proportion of groundwater samples suitable for irrigation and unsuitable for irrigation was 2:3. The groundwater quality in the irrigation area was affected by the combined effects of evaporation-concentration and mineral dissolution, original geology conditions, and human activities. In addition, it was also affected by cation exchange.

In response to the serious problem of the tight supply and demand of water and grain in Ningxia, an experiment on the effects of water stress during the critical growth period of corn was carried out to provide a theoretical basis for regional food security and rational irrigation. In this study, the water stress test was carried out with the corn ‘Xianyu556’ as the test material. The test set up a control group CK (no coercion), and 4 treatments (water stress from tasseling stage to grain filling stage, T1; water stress from small bell mouth stage to tasseling stage, T2; water stress from small bell mouth stage to grain filling stage, T3; water stress from small bell mouth stage to grain filling stage with added irrigation, T4). The soil water content and photosynthesis were measured according to the maize development stage and irrigation time. The yield structure was measured at the mature stage, and the Water Use Efficiency (WUE) and harvest index (HI) were calculated. The results showed: water stress from small bell mouth stage to grain filling stage limited maize photosynthesis due to stomatal factors caused by drought stress. The net photosynthetic rate of the treatment of added irrigation in corn filling stage was increased by 62.7% than that of CK. Ear length, ear diameter, ear weight, number of rows per ear, grain weight per ear and grain number per ear were significantly decreased by 22.6%, 24.9%, 63%, 28.7%, 67.7% and 71% in T3 treatment compared with CK treatment. In addition, plant height, ear stem, heading rate, grain yield and harvest index were also significantly decreased. Combined with yield and water use efficiency, the WUE of T1 and T2 treatments was higher than that of CK. The yield of T2 was 18.9% lower than that of CK, the yield of T1 was 1.3% lower than that of CK, and the WUE was 36% higher than that of CK. The yields of T3 and T4 were significantly lower than those of CK. T4 treatment did not effectively increase maize yield, but decreased WUE. The moisture content of leaves and sheathing of maize in all treatments had the same trend, but had no significant difference before grain filling stage, and showed T3/T4>T1>T2>CK from milking to maturity stage. The moisture content of stem and ear of CK, T2 and T4 showed the same trend. According to the comprehensive results, to ensure the best corn yield, high grain structure and water-saving irrigation, it is necessary to comprehensively balance the water from the small bell mouth stage to the filling stage.

The aim of this study was to explore the regulation mode of water and fertilizer for sugarcane efficient production in Guangxi. Sugarcane of Liucheng 05136 was selected as the research object, and four irrigation schemes (T1:6.53 m³/hm²; T2:8.70 m³/hm²; T3:10.87 m³/hm²; T4:13.05 m³/hm²) and 5 fertilization schemes (F0: no fertilization; F1: reapplication at tillering stage; F2: reapplication at tiller - extended stage; F3: reapplication at extended stage; F4: reapplication at elongation-maturity stage) to analyze the response rule of sugarcane agronomic traits, yield and water and fertilizer utilization efficiency to water and fertilizer regulation. The results showed that F3 and F4 treatments significantly increased the effective stem number of sugarcane, and T2 treatment significantly increased the single stem weight, plant height and stem diameter of sugarcane. Among the quantitative fertilizer applications throughout the reproductive period, the best sugarcane yield (962.25 kg/hm²), fertilizer utilization efficiency (48.20%) and irrigation water utilization rate (10.47 kg/hm²/mm) were achieved under the F3 treatment with different drip irrigation fertilizer application levels for increasing elongation (favoring the peak of fertility). The effect of irrigation amount on sugarcane yield and nutrient uptake and utilization was not obvious. The utilization rate of sugarcane irrigation water was significantly increased under T1 and T2 treatments. T2 and F3 treatments were the optimal combination, that is, the water and fertilizer regulation mode of sugarcane water-saving and yield increasing was the irrigation amount of 8.70m³/hm² and the heavy fertilizer application in the extended period. The results can provide scientific basis for sugarcane water and fertilizer management in Guangxi.

Aiming at the problem that the current irrigation water distribution channel system lacks comprehensive performance index as the basis for scheme comparison and parameter optimization, a comprehensive index considering water level, flow rate, gate opening and stable transition time was proposed to measure the effect of channel control. The indicator is calculated based on the improved radar chart. And the improvement lies in the standardized processing of multiple optimization targets with the average value of samples. Then, the processed indicator is taken as the distance from the center to each vertex when drawing the chart, and the area of the radar chart is the value of the newly proposed comprehensive indicator. Taking the fourth main canal of Zhanghe Irrigation Area as an example, the effectiveness of the proposed indicator as the optimization objective of PI control is verified. The results show that the comprehensive performance of the system is close to the optimal after two-step optimization, and the proportional parameter is 0.2, the integral parameter is 8.2, the maximum water level deviation is 0.0288 7 m, the cumulative amount of water level deviation is 0.195 5 m, and the cumulative amount of flow change is 0.772 0 m3/s. The cumulative amount of gate action is 0.952 4 m, and the stable transition time is 42 min. The cumulative amounts of water level, flow and gate opening in the transition process and the stable transition time are small enough to meet the expected control effect. The comprehensive index proposed in this study can be used for the evaluation and selection of different control schemes, and also for the optimization of control algorithm parameters. The multi-objective optimization method based on the comprehensive index has certain reference value for the automatic control of water distribution channel system in irrigated area.

Based on historical meteorological observation data from 107 stations in the Huang-Huai-Hai region, as well as daily temperature and precipitation under two scenarios (SSP2-4.5 and SSP5-8.5) of 11 General Circulation Models (GCM) in Sixth Intercomparison Project Phase 6 (CMIP6), this study analyzed the temporal and spatial evolution characteristics of heat and extreme precipitation during the growth period of summer maize in next two stages (2021-2050 and 2051-2080). The results show that quantile-based bias correction method (QM) can effectively eliminate the systematic bias in GCMs. Under SSP2-4.5 scenario, multi-model average maximum temperature during the growth period of summer maize will increase 1.38 ℃ and 2.52 ℃ respectively in next two stages. While under SSP5-8.5 scenario, it will increase 1.76 ℃ and 3.58 ℃. At the same time, Killing Degree Days (KDD) with daily maximum temperature exceeding 35 ℃ under SSP2-4.5 scenario will increase 16.4 ℃?d and 41.3 ℃?d respectively in the next two stages. While under SSP5-8.5 scenario, it will increase 23.1 ℃?d and 75.8 ℃?d. Among all the regions, Henan Province has the most prominent increase. Multi-model average precipitation during summer maize growing period under SSP2-4.5 scenario will increase 12.27 mm and 26.39 mm respectively for future two stages. While under SSP5-8.5 scenario, it will increase 9.86 mm and 39.54 mm. The number of heavy rain days also shows an increasing trend. Under SSP2-4.5 scenario, it will increase 0.09 days and 0.18 days respectively in next two stages, while under SSP5-8.5 scenario it will increase by 0.07 days and 0.29 days.

In order to explore the effects of different regulated deficit irrigation on walnut growth and high yield under drip irrigation, the optimal regulated deficit irrigation system was obtained through studying the changes of walnut growth index and yield. A total of three levels (ET ₀, 75%ET ₀, 50%ET ₀) were set in this experiment, with a total of five treatments, each with three replicates. Among them, W0 was the control group (CK), W1 was a continuous moderate and mild regulated deficit in stage Ⅱ and Ⅲ, W2 was stage Ⅱ with mild dysregulation, W3 and W4 were continuous moderate and mild dysregulated in stages Ⅰ, Ⅱ and Ⅲ. It was found that W3 treatment had the greatest inhibition on shoot growth, which was reduced by 14.7%, 28.93% and 18.33% compared with W0 at the end of Ⅰ, Ⅱ and Ⅲ, respectively. Mild regulated deficit at stage Ⅱ had the least damage to leaf cells at this growth stage, and SPAD value could return to normal level in the later stage under normal irrigation, but not under other treatments. At the end of Ⅱ, the longitudinal and transverse diameter and volume of fruits in each treatment were as follows: W3 > W1 > W4 > W2 > W0, and at the end of the growth period, it showed W2 > W0 > W4 > W1 > W3. Through the comprehensive study of the growth characteristic index and yield under different deficit regulation treatments, it was determined that W2 treatment could play the effect of pruning and increasing the yield.

Through the field positioning experiment, the dynamic change characteristics of farmland water and salt, cotton yield and water use efficiency under conventional drip irrigation cotton planting under membrane are studied, which is of great significance to prevent soil salinization and improve the efficiency of water and soil resources use. The results showed that drip irrigation under mulch mainly affected soil moisture in cotton tillage layer, but did not produce deep leakage. With the increase of soil depth, the soil moisture content in the 100 cm soil layer showed a trend of "first increasing, then decreasing, then increasing". The soil moisture content reached 25.16% in 100 cm soil layer. With the increase of cultivation years, the salt content in the 0~100 cm soil layer showed an increasing trend, and the accumulation of salt content between drip irrigation belts was more significant than that between drip irrigation heads. After harvest in 2021, the salt content in the 0~10 cm soil layer between drip irrigation belts reached 1.63 g/kg. The grain cotton yield decreased with the increase of the year, and the grain cotton yield was between 4 398.3 to 4 970.1 kg·hm^-2. It is suggested that the planting structure and irrigation method should be adjusted from the fourth crop to create a good water-salt environment for crop growth.

In order to study the effects of deficit irrigation on physiology, growth, quality and water use efficiency of greenhouse tomato production during autumn and winter, a deficit irrigation experiment was carried out with ‘Shengfeng No. 5’ tomato as experimental material. From flowering and fruit stage to harvest stage, 0~4 times irrigation were taken on the experimental materials respectively, corresponding to treatments T1, T2, T3, T4 and T5. The data of air temperature, humidity and soil water content in the greenhouse was observed and recorded, and the comprehensive evaluation system of tomato growth was constructed by using analytic hierarchy process (AHP). The first-class indexes are physiology index, growth index, quality index and index of water use efficiency (WUE). The physiological index includes net photosynthetic rate, stomatal conductance, transpiration rate, leaf nitrogen content and chlorophyll. The growth index includes root-shoot ratio and biomass. The quality index includes lycopene, Vc, total sugar and titratable acid. And the WUE index includes WUE_y and WUE_b . The entropy weight method was applied to calculate the weight of secondary indexes, and the TOPSIS evaluation method was applied to sort them. In the physiological index evaluation system, the relative proximity of T3 was 0.769, which was the closest to the ideal solution. The relative proximity of T1 was 0.555 in the evaluation system of growth index, and it was the closest to the ideal solution. In the fruit quality evaluation system, the relative proximity of T5 was 0.617, which could be considered as the best treatment. And in the WUE index, T1 was the best treatment. This research applied Fuzzy Borda method to evaluate the order value and ranking information of the first-class indexes, and the fuzzy Borda scores of T1~T5 wee 8.87, 4, 5.14, 5.77 and 5.15, respectively. The results showed that no water treatment from flowering and fruit stage to harvest stage (except for the first watering and water applied in water-soluble fertilizer) of greenhouse tomato production during autumn and winter could not only make the plant grow well, but also significantly improved the water use efficiency, which had the best performance in the comprehensive growth evaluation system of tomatoes. This irrigation treatment system effectively reduced the water consumption of greenhouse tomato production during autumn and winter in Hebei province, and realized the improvement of quality and efficiency in agriculture.

In order to construct the vegetation construction of rainwater bioretention system in loess distribution area according to local conditions, five groups of biological detention system simulation devices were constructed with Iris, Hemerocallis, Sedum, Ophiopogon and non-plant control group as the research objects to study the effects of plants on the long-term nitrogen removal function of the biological detention system. The results showed that there was no significant difference in the distribution of NH₄ ⁺-N in the system fillers under different plant treatments, and the content of NH₄ ⁺-N in the system fillers decreased with the increase of running time. The average NH₄ ⁺-N removal rate of 5 treatments was as follows: Sedum (91.84%) > NO plants (91.65%) > Ophiopogon (91.30%) > Hemerocallis (90.79%) > Iris (87.90%). The distribution of NO₃ ^--N in system fillers under different plant treatments was related to root length. The longer the root, the lower the content of NO₃ ^--N in system fillers. The average NO₃ ^--N removal rate of 5 treatments was as follows: Iris (29.92%) > Sedum (14.88%) > Hemerocallis (7.16%) > Ophiopogon (-13.9%) > NO plants (-24.19%). The NO₃ ^--N content of fillers before influent was significantly correlated with the effluent concentration of NO₃ ^--N in each system (P <0.01, R²=0.679). Compared with no plants, plant treatment can increase TN removal rate through plant absorption and denitrification, and reduce TN normalized ratio in effluent.

In order to improve the efficiency of fertilizer application in wheat and reduce soil environmental pollution, two irrigation methods (drip irrigation and border irrigation) and three fertilization treatments were set for the field experiment, and the fertilizer application rates were 100%, 80% and 60% of the nitrogen application rate for high yield, respectively, to analyze the distribution of nitrogen and pesticide in wheat under different irrigation methods and their effects on yield and utilization efficiency of water and fertilizer. The results showed that the NO₃ ^--N content in soil increased with the increase of N application rate, and the NO₃ ^--N content in soil under drip irrigation was lower than that under border irrigation. With the passage of growth period, NO₃ ^--N content in soil decreased. Drip irrigation could reduce the leakage of pesticides into the deep layer, and the residual amount of bensulfosulfonon in 0~100 cm soil was reduced by 48.32% compared with border irrigation, but it was not conducive to the decomposition of dimethyl tetrachlorosodium pesticides in the soil. Under different irrigation conditions, plant height, 1 000-grain weight and yield of wheat increased with the increase of fertilizer application rate. Compared with border irrigation, drip irrigation promoted stem and leaf dry matter output and dry matter conversion, and improved wheat yield and water and fertilizer use efficiency. Compared with border irrigation, drip irrigation increased wheat yield, water use efficiency and nitrogen partial productivity by 7.09%, 41.56% and 57.58%, respectively. Therefore, the best fertilizer application rate under drip irrigation is 1 500 kg/hm².

Vegetation plays an important role in the turbulence that affects rivers. In order to clarify the turbulent flow characteristics under the combined distribution of vegetation in the patch, the CFD tool FLUENT and Reynolds stress model were used to design four different vegetation combinations, and the flow characteristics of the longitudinal discontinuous rigid vegetation patch occupying half of the width of the channel were numerically simulated. The results show that: ①Due to the existence of vegetation, the velocity of vegetation area is significantly lower than that of non-vegetation area, and the velocity difference between vegetation area and non-vegetation area increases with the increase of vegetation coverage. Therefore, the vegetation area with larger vegetation coverage is more conducive to sediment deposition and the growth of aquatic vegetation. ②The velocity difference between the non-vegetated area and the vegetated area is large, resulting in a free shear layer at the interface, resulting in a strong mass and momentum exchange in this flow area. ③The turbulence in the vegetation area was significantly larger than that in the non-vegetation area, and increased with the increase of patch density in the vegetation area.