The presence of gravel in soil can change the process of soil moisture migration in varying degree and has an important impact on soil hydrological process. In this paper, the red soil in the key provincial soil erosion control area in the upper reaches of Cao 'e River was taken as the research object, and the soil infiltration characteristics of red soil with different gravel contents (0%, 10%, 20%, 30%) were studied by indoor vertical one-dimensional constant head soil infiltration experiment. Kostiakov, Horton and Philip models were used to fit the infiltration process. The results showed that the initial infiltration rate, stable infiltration rate and average infiltration rate all increased with the increase of gravel content, but not continuously with the increase of gravel content. There were no significant differences in initial infiltration rate, stable infiltration rate and average infiltration rate of red soil with 20% and 30% nested gravel content (P < 0.05). The influence of gravel nesting on soil water infiltration is in many aspects. It is shown in the following aspects: with the increase of gravel nesting content, it is easy to form soil large pores, which is conducive to the generation of dominant flow in the soil, thus promoting infiltration, but also makes the water infiltration path curved complex, so as to limit infiltration. It takes a long time to reach the stable infiltration rate for the gravel-containing red soil, and the changes in the three stages of transient, leakage and stable infiltration are clear. While for the red soil without gravels, the time to achieve the stable infiltration rate is short, and the soil water infiltration curve is relatively stable. The Horton model has the best fitting effect for the red soil infiltration process without gravel and under the condition of gravel content of 10 % and 30 % nested. The Philip model can better reflect the fitting effect for the red soil infiltration process under the condition of gravel content of 20 % nested. On the one hand, this study can enrich the water infiltration mechanism of red soil with gravel nesting, on the other hand, it can also provide scientific basis for soil erosion prevention and comprehensive management, and strengthen ecological restoration in soil erosion areas.

The simulation of the distribution and transfer of photosynthetic products under water stress is an important basis for crop cultivation and irrigation management. Based on the experimental data under water stress of Shanxi Provincial Huoquan Irrigation Experiment Station for three consecutive years (2018, 2019 and 2020), in this study, two methods of distribution coefficient and distribution index were used to simulate the distribution and transfer of winter wheat photosynthetic products, and the coefficient of certainty R² and relative error RE were used as indicators to evaluate the simulation results. The results show that: ①Water stress has an influence on the balance coefficients of stem-leaf, ear-stem and root-canopy. It can decrease stem-leaf ratio and increase ear-stem ratio and root-canopy ratio. ②Water stress has a certain influence on the distribution coefficient, while it has little effect on the distribution index. ③The two methods have no effect on the simulation results of the dry matter on the ground, but for the simulation of crop yield, the distribution index method is better than the distribution coefficient method. ④Water stress increases the transfer rate of photosynthetic products in stems, however, it has no obvious impact on the transfer rate of photosynthetic products in leaves. It can be concluded that: in the simulation of crop growth process, both the effects of distribution coefficient method and distribution index method are good. On the whole, the distribution index method is better than the distribution coefficient method. However, the distribution coefficient method has strong mechanism and is helpful to understand the growth process of winter wheat.

Revealing the propagation characteristics of precipitation uncertainty in hydrological process is the key element of hydro-meteorological forecasts, which can provides strong support for the improvements of watershed water resources management and agricultural irrigation. In this paper, the precipitation prediction from 5 different TIGGE center(CMA、CMC、ECMWF、NCEP and UKMO) were used to drive the distributed Xinanjiang model to generate the runoff ensemble forecast in flood season of The Fujiang River basin from 2010 to 2013.On this foundation, the propagation characteristics and temporal changes of precipitation uncertainty were analyzed quantitatively in accuracy and sharpness. The results indicated that both accuracy and sharpness of precipitation forecasts were significantly improved after hydrological process in different years and different prediction periods. However, with the prolongation of prediction period, the improvement effect on precision decreases gradually, while the improvement effect on sharpness increases continuously.

The prevalence of snowpack and freeze-thaw cycles in the seasonal freeze zone will lead to more complex soil moisture transport in the unsaturated zone. In view of the above phenomenon, this paper designed and carried out unsaturated soil in-situ observation experiment and in-lab soil column observation experiment under the coupling effect of snowpack and freezing-thawing to explore the influence of different depths and different snowpack conditions on soil water transport, and then quantitatively calculated the change rule of snowmelt infiltration under the change of snowpack conditions. The results showed that: soil water transport under snowpack was affected by meteorological conditions, snow, depth, soil temperature and salinity, etc; Thick, high-density snow had a good effect on soil insulation, melting fronts are deeper and faster; When the thickness of the snowpack increased by 2 times, the snowmelt infiltration at this time was 2 times of the natural snowmelt infiltration, when the snow layer density increased by 2 times, the snow melt infiltration was 1.22 times of the natural snow density. Therefore, a reasonable change in snow density can affect the infiltration of water recharge in the seasonal freeze zone and achieve the purpose of reasonable use of soil water resources.

Accurate estimation of evapotranspiration (ET) is critical for water resources management and drought assessment. This study evaluated the performance of two integrated tree class algorithms, XGBoost (XGB) and Random Forest (RF), on estimaing farmland ET at different time scales. The input data of the model were meteorological observation data from the flux site, leaf area index (LAI) product data from MODIS satellite, and ERA reanalysis data. The results showed that the PBIAS of the two sites was within 5%, and there was no overestimation or underestimation on the whole. Adding LAI on the basis of meteorological data could improve the prediction accuracy of the model, but there was little difference between meteorological data and reanalysis data as input. At the half-hour scale and daily scale, XGB model was superior to RF model on the whole. This study can provide a reference method for the accurate estimation of ET.

The scarcity of water resources disturbed by climate change makes the sustainable utilization of water resources in agriculture face a crisis. Water-saving agriculture is the main way of agricultural transformation in modern society and the fundamental way out of sustainable development. Heihe River Basin is the second largest inland river in China, and the oasis in the middle reaches is an important food production base in China. Understanding the crop planting information and crop water demand characteristics in Heihe River Basin is of great significance for guiding agricultural efficient water use in arid and semi-arid areas and national food security. Based on Google Earth engine (GEE) cloud platform, by using sentinel-2 image and combined with the phenological characteristics of crops in Heihe River Basin to select the image data from June to September, the feature optimization was completed according to the importance of crop phenological characteristics. Random forest, support vector machine, decision tree and voting classifier were used to classify crops and compare the results. Finally, the CROPWAT model was used to estimate the crop water requirement and irrigation water consumption in the Heihe River Basin. The results show that:①GEE can quickly complete the preprocessing of image data, such as cloud removal and feature construction;②The accuracy of land classification results based on decision tree classifier is 82.5%, and the average Kappa coefficient is 0.73. The water demand and irrigation water consumption of crops in each period were estimated. The constructed classification system and crop water demand estimation provide a new idea for accurate management and irrigation control system.

Evapotranspiration (ET) is crucial in the hydrological processes, and the accurate estimation of ET is of helpful for water resources management and drought assessment. In this study, after measuring the meteorological factors and latent heat flux by eddy covariance method on alpine potentilla fruticosa meadow at Qilian Mountain (Site I), the average daily ET of meadow was calculated by Penman-Monteith (PM) model, Priestley-Taylor (PT) model and Shuttleworth-Wallace (SW) model in 2003-2010. Based on the meteorological data for Haibei Animal Husbandry Meteorological Experimental Station (Site II) in Qilian Mountain in 2003-2014, the optimized estimation model of meadow ET in Site I was verified by water balance method. Moreover, the determination meteorological factors for ET were analyzed. The results showed that the average daily ET increased in spring, and reached peak value at summer with annual average of 1.58 mm/d at Site I. In the comparison between the estimated ET and the measured ET in Site I, the determination coefficient (R² ) of PM, PT and SW was 0.79, 0.83, and 0.84, respectively, the consistency index (d) was 0.89, 0.85, and 0.90, and the absolute average error (MAE) was 0.46 mm/d, 0.72 mm/d, 0.43 mm/d, respectively, which indicated that the SW model was suitable for evaluating the daily ET for the whole growing season. The annual average daily ET estimated by the SW model was 1.35 mm/d in Site II and the determination coefficient (R² ) between the estimate ET and the actual ET calculated by the water balance method was 0.87. The order of the actual ET of flux station and the coefficient of determination of environmental factors (R ²) was net solar radiation>temperature>relative humidity>wind speed in Site I, indicating that the main determinant factor of evapotranspiration of alpine meadow was solar net radiation (R ²=0.65). This study simulated the ET of alpine meadow and provided a scientific basis for studying the ecological water consumption of alpine meadow in Qilian Mountains.

Aiming at the problem of easy blockage of the emitter, the labyrinth channel irrigator was used as the research object, the SolidWorks software was used to complete the modeling design of the labyrinth channel. Combined with computational fluid dynamics software Ansys Fluent simulation, the hydraulic performance of labyrinth channel under 0.10 MPa, 0.12 MPa, 0.14 MPa, 0.16 MPa and 0.18 MPa pressure was analyzed. The pressure, flow velocity, turbulent kinetic energy and particle trajectory were studied to reveal the internal flow mechanism. The results showed that:①The flow velocity was affected by the operating pressure of the system, but did not completely increase with the increase of the pressure, and the response relationship between the flow velocity and the pressure was effective in a certain range; ②The pressure drop gradient inside the flow passage increased with the increase of the system operating pressure, and negative pressure appeared at the outlet of the flow passage, which affected the performance of the emitter; ③The turbulent kinetic energy in each region was basically stable and obviously different. The turbulent kinetic energy in the vortex region decreased with the increase of the operating pressure of the system, while the turbulent kinetic energy in other regions increased.④The larger the particle size was, the worse the water quality was, and the greater the probability of blockage was. Increasing the operating pressure of the system was conducive to the migration of small particles, and easy to cause the deposition of large particles, resulting in the blockage of the emitter. The simulation results showed that under different operating pressure conditions, the hydraulic characteristics of different flow channel units of the irrigator had similar laws, and its anti-clogging performance was affected by the operating pressure of the system, and was improved in a certain pressure range.

In order to study the impact mechanism of biochar application on methane emissions from water-saving irrigation paddy fields, fluorescence quantitative PCR method was used to study the effects of different levels of biochar application on the abundance of mcrA and pmoA genes in water-saving irrigation paddy soil. The results show that biochar application can increase the pmoA and mcrA genes abundance of water-saving irrigation paddy soil. The effect of high-volume biochar addition in the milk maturity stage is more significant, while the medium-level biochar addition has a more significant effect in the tillering stage and jointing and booting stage. Control irrigation can significantly increase the pmoA and mcrA genes abundance in paddy soil during the tillering stage and milk maturity stage. Control irrigation can significantly increase the pmoA/mcrA ratio (p<0.05) in the tillering stage and milk maturity stage, and the application of biochar can significantly increase the pmoA/mcrA ratio (p<0.05) of paddy soil in the milk maturity stage. Control irrigation and biochar application can increase the methane oxidation capacity of the soil and reduce methane emissions from the paddy soil. In summary, both biochar and control irrigation can increase the gene abundance of methanotrophs and methanogens in paddy soil to a certain extent. At the same time, the promotion effect on methanogens is less than that of methanotrophs. Changing the quantity and ratio of pmoA and mcrA genes in soil can help to regulate soil methane emission in paddy field.

Domestic reclaimed water contains a large number of nutrient elements necessary for plant growth, which is a good water source for urban green space irrigation and has a high utilization value for alleviating urban water shortage. In order to reveal the impact of domestic reclaimed water irrigation on the rhizosphere soil nutrients of common cold-season grasses, this study used three types of water quality (i.e., fresh water, reclaimed water, and mixed water composed of 50% of fresh water and 50% of reclaimed water) for turf grass (Poa pratensis) irrigation in an entire year. The results showed as follows: ①Irrigation with different water quality changed the vertical distribution of nutrient elements in the soil, and the total nitrogen, the contents of alkali-hydrolyzable nitrogen and available potassium first decreased and then increased with the increase of soil depth.②Under T0, T1 and T2 treatments, the contents of organic matter and NO₃ ^- in the soil decreased first and then increased with the increase of soil depth, and the contents of organic matter in 0~10 cm soil layer were much higher than before (7.8 mg/kg), which were 12.7 g/kg, 13.4 g/kg and 13.5 g/kg, respectively. Among them, the NO₃ ^- content in 0~10 cm soil layer treated by reclaimed water reached 27 mg/kg, which was much higher than 7 mg/kg of mixed water and clean water.③Under reclaimed water irrigation, the soil volumetric water content was the lowest, and the fluctuation range of soil volumetric water content at 90 cm layer was the lowest (0.218 cm³/cm³ to 0.268 cm³/cm³). Compared with irrigation with clean water, nutrients in reclaimed water could be absorbed by plant roots to promote the growth of turfgrass. However, if the reclaimed water is used for long-term irrigation or the reclaimed water concentration is not controlled, a large number of chemical substances in the water will affect the soil porosity and have a certain impact on the soil.

Straw returning is one of the common agricultural measures to improve soil quality in Northwest China. In order to clarify the effects of different straw returning methods on the microstructure and physicochemical properties of saline-alkali soil in Xinjiang. In this study, a field experiment was carried out in 2020. A total of 5 treatments, including the treatment of non-returning field as the control, cotton straw soil-turning and returning (H1), rape straw soil-turning and returning (H2), cotton straw mulching and returning (F1), and rape straw mulching and mulching (F2) were set up to analyze the changes of electrical conductivity, water content, organic matter and particle size distribution of aggregates in 0~20 cm soil layer. Scanning electron microscopy (SEM) was used to investigate the changes of soil microstructure. The results showed that compared with CK, the conductivity of H1 and H2 treatments decreased gradually with the increase of returning time and the water content gradually increased, and the effects were better than those of F1 and F2 treatments, respectively. On the 75th day, the conductivity of H1 and H2 treatments decreased by 5.30% and 3.89%, and the water content increased by 8.93% and 7.85%, respectively. Compared with CK, soil organic matter in H1 and H2 treatments increased by 30.90% and 29.80%, respectively. In addition, H1 and H2 treatments reduced the proportion of aggregates <0.053 mm in soil, and the proportion of aggregates of 0.25~2.00 mm was increased by 3.71% and 4.60%, respectively. Compared with the treatments of F1 and F2, the treatments of H1 and H2 increased the soil flake microstructure, the particles changed from surface to surface contact to direct point contact, and the number of soil pores was increased. In conclusion, straw soil-turning is more conducive to improving soil particle microstructure and soil aggregate particle size composition than mulching, and enhances the effect of salinity reduction and water retention. The study provides theoretical support for straw returning to fields in Xinjiang.

The development of new water-saving irrigation technology and more efficient use of existing water resources are the inevitable choices to solve the agricultural water crisis and develop modern agriculture. This study was based on the greenhouse pot experiment. "Ladi No. 1" was used as the test variety. A total of five treatments (CK, S10-1, S10-2, S15-1 and S15-2) were set, including two dosage of super absorbent polymers (0.1% and 0.2% of dry soil weight) and two burial depths of super absorbent polymers (10 and 15 cm, layer application), and no super absorbent polymer (CK) was applied as a control. The effects of different super absorbent polymers management modes on the growth, yield and water use efficiency of pepper were studied by observing soil moisture and growth indexes of pepper during growth period and calculating the indexes of yield, water use efficiency and economic benefit, so as to explore the super absorbent polymers management mode for efficient production of pepper. The results showed as follows:①Compared with CK, the application of super absorbent polymers significantly promoted the growth and dry matter accumulation of pepper, and improved the yield, water use efficiency and economic benefit of pepper;②Under different super absorbent polymer management modes, the growth and yield indexes of pepper increased with the increase of super absorbent polymer dosage, but decreased with the increase of super absorbent polymer buried depth;③Among all the treatments, the treatment of shallow-buried and high-application super absorbent polymer (S10-2) had the best performance, with the highest plant height, stem diameter, leaf area index, total dry matter accumulation, economic yield and water use efficiency, which were increased by 8.17%, 8.69%, 6.43%, 20.15%, 42.22% and 85.71%, respectively, compared with CK. Comprehensive analysis results of yield, water use efficiency and economic benefit showed that S10-2 treatment could be recommended as a water-saving, high-yield and high-benefit super absorbent polymer management mode for greenhouse pepper.

The soil water and salt transport in arid regions has obvious seasonal characteristics, but there are differences in the effects of different tree species on water and salt transport and soil nutrients in saline-alkali soil. In this paper, the effects of different tree species on soil water and salt transport and nutrients were studied by using the method of field investigation and indoor detection. The results showed that: ①Soil moisture in salix psammophila and salix matsudana ‘9901’ community migrated downward and accumulated in the soil layer below 60 cm with time lapse, while soil moisture in tamarix chinensis community migrated upward from 60 cm. Soil salinity in salix psammophila, tamarix chinensis and salix matsudana ‘9901’ community changed from wave type to “V”type distribution, and soil salinity in tamarix chinensis community was the lowest.②After planting trees, the soil pH was lower than that of bare area, and the soil pH of tamarix chinensis community was the lowest.③Planting salix matsudana ‘9901’ could increase the contents of soil organic matter and available P in 0-40 cm soil layer. The results reveal the effects of different tree species on soil water-salt transport and nutrients in Yinbei region of Ningxia, which can provide a theoretical basis for vegetation restoration in saline-alkali land of similar regions.

In order to explore the effects of fertilization concentration and pressure head on soil water-nitrogen distribution under moistube irrigation, an indoor soil box simulation experiment was carried out. The experiment set two pressure heads of H1(1.0 m) and H2(1.5 m), and four fertilization (calcium ammonium nitrate) concentrations, including N0 (without fertilization), N3(300 mg/L), N6(600 mg/L) and N9 (900 mg/L), and 2×4 two-factor analysis was performed. The wetting front migration, cumulative infiltration, soil moisture and the variation of nitrate nitrogen content were measured and analyzed. The results showed that under the conditions of 1.0~1.5 m water head and 0~900 mg/L fertilizer concentration, the migration distance, migration speed, cumulative infiltration, soil moisture content and nitrate nitrogen content in the same position of the wetting body increased with the increase of pressure water head and fertilizer concentration. The migration distance of wet front has a power function relation with time (R ²>0.9), and the migration rate slowed down with the experiment progress. The content of soil moisture content was the highest near the moist-tube and gradually decreased in the distance. The position of the maximum soil moisture content gradually moves down with the infiltration progress. The nitrate nitrogen accumulated in the distance. Contrary to the distribution law of water content, nitrate nitrogen was easily lost with water, and the maximum value occurred at distant deep soil. When the pressure head was 1.5 m and the calcium ammonium nitrate concentration was 900 mg/L, the wetting front moved the fastest, and the moisture content and nitrate nitrogen content in the wetting body were the highest, which was a more suitable treatment for agricultural planting.

Water consumption per 10 000-yuan GDP is one of the current important index to reflect WUE (water use efficiency) in China. However, the rapid growth of regional GDP will conceal the inefficient water consumption targets, resulting in insufficient reflection of the imbalance of regional proportion of water consumption and sector’s water efficiency. After analyzing the proportion of water consumption of "domestic, ecology, production" and "primary, secondary and tertiary sectors", a new measurement of WUE-comprehensive water consumption per 10 000-yuan GDP was designed based on different proportion of sector’s water consumption. Taking the statistical data about water consumption of China's provincial region in 2019 as an example, the effectiveness and rationality of the "new measurement" were analyzed and demonstrated by adopting index correlation analysis, "K-means" clustering, hierarchical clustering, and the similarity analysis of sets. The main conclusion was that the "new measure" has advantages in comprehensively reflecting regional WUE, which could better identify the objects of inefficient water consumption, and find the key regions or sectors needing to further cut down the amount of water. Using the "new measure"，the spatial differentiation characteristics of China's WUE(2019) showed that: the regional WUE was higher in provinces lacking water resources such as Beijing, Tianjin and the lower Yellow River, as well as regions lacking water supply projects such as Guizhou. On the contrary, regional WUE was low in Xinjiang, Tibet and some underdeveloped provinces in the north, which had great potential in saving water. The agricultural WUE of developed provinces was relatively low, such as Shanghai, Jiangsu and Guangdong, as well as central provinces such as Anhui, Hunan and Jiangxi, which could save more water than other similar provinces. The "new measurement" can be used as an alternative indicator of the current "water consumption per 10 000-yuan GDP" to improve the identification and transformation of the inefficient water consumption targets.

In order to alleviate the adverse effects of extreme climate conditions on grape growth environment and fruit quality in the TuHa area, ‘Thompson Seedless’ grapes were used as materials and micro-spraying was set at different heights of grape trellages (WP1:50 cm above the trellage, WP2:50 cm below the trellage, WP3:30 cm above ground), and conventional drip irrigation was used as control treatment (CK) to analyze the effects of different treatments on temperature and relative humidity under grape trellage and grape quality, in order to provide a basis for local grape quality production and cultivation. The results showed that compared with the control treatment, the daily maximum temperature decreased by 1.15~2.94 ℃, and the daily minimum relative humidity increased by 2.32%~3.21%. Six hours after the micro-spray was turned on, the average temperature decreases by 1.34~2.62 ℃, the average humidity increases by 2.93%~3.99%, the temperature difference decreases by 1.80~3.40 ℃, and the humidity difference decreases by 0.50%~2.61%. The temperature and relative humidity were linearly negatively correlated. Micro-spraying treatment could significantly increase the content of soluble solids, soluble sugar and reduced Vc in fruit, and reduce the total acid content in fruit. The soluble solid content of WP2 treatment was 22.2% higher than that of CK, and the sugar and acid content was 17.28 higher than that of CK, and the difference was extremely significant. After comprehensive analysis of temperature, relative humidity and fruit quality, it was found that spraying water 50 cm below the trellage at 14:00 every day for 1 hour during fruit expansion period could improve the quality of ‘Thompson Seedless’ grape, which was suitable for promotion in Tuha region.