Irrigation Schemes Research Articles

Performance of Basin and Bubbler Irrigation Systems under River Nile State Conditions

This study was conducted in the Jordanian Bashair project,River Nile State, during two seasons (2007 and 2008) to evaluate theperformance of irrigation systems applying different amounts of irrigationwater. The treatments were surface irrigation method (basin irrigationsystem) and localized irrigation system with two types of distributors:locally made bubblers and imported bubblers. The irrigation wateramounts were given as percentages (50%, 75% and 100%) of date palmwatering requirement (ETc). ETc was obtained from the means of theprevious thirty years, using CROPWAT4 WINDOWS. The performanceof the irrigation system was evaluated with reference to the applicationand storage efficiencies and distribution uniformity. The experiment wasorganized in a split plot design with three replicates. The irrigationsystems showed negative effect on distribution uniformity and positiveeffect on application and storage efficiencies. The locally made andimported bubblers revealed highly significant (P ≤0.01) differences withapplication and storage efficiencies, while there was no significantdifference between them. The 50% ETc recorded high significant valuesof application efficiency, but less values of storage efficiency anddistribution uniformity. Interaction of the irrigation systems and amountsof water showed positive effect, whereas locally made bubblers showedhigher values of application and storage efficiencies with 50% and 100%ETc, respectively. On the other hand, the basin irrigation system gavehighest values of distribution uniformity with 75% and 100% ETc .Hence,it was concluded that using bubbler irrigation system would give highirrigation efficiency, thus saving water for other agricultural activities.

Fodder Preparation Practices Adopted by Community Subsistence Farmers in Zimbabwe in the Face of Climate Change: A Case Study of the Garanyemba Community Ward 13 in the Gwanda District, Matabeleland South Province.

The study identifies methods and practices adopted by communal subsistence farmers in preparing fodder for their livestock in the face of climate change. The purpose is to enhance fodder availability in the Garanyemba Ward 13, Gwanda District in Matabeleland South Province, Zimbabwe. Explored are challenges that affect methods / practices of fodder preparation on which livestock depends; without which communities cannot survive. The study employed a mixed methods research methodology; gathering data through face-to-face in-depth semi-structured interviews and questionnaire. Analysis was through descriptive statistics, thematic and content analysis methods. Findings suggest that Garanyemba communal farmers are overwhelmed with numerous problems that affect fodder availability. Mountains and inselbergs have deprived the Ward of its agricultural land and crop residues; a critical component of fodder. Climate change has caused droughts, low rainfall, water shortage, non-availability of grass and premature drying of rivers and wetlands which are the main sources of water. This has caused serious shortage of fodder; and affected livestock productivity. These challenges have driven communities to prepare fodder to protect livestock against feed shortage; and losses during dry seasons. Cutting grass, crop residues, the ‘cut and carry’ system, ‘emilageni’ – the ‘lagisa’ system; and novel initiatives comprise the main methods of fodder preparation. Water harvested through sand dams helps to grow fodder. Training has improved communities’ skills to make fodder. Recommendations include construction of micro–dams, more sand dams and piping water from the Thuli River to avail water; and start irrigation schemes to grow fodder. Workshops and refresher courses on fodder preparation are encouraged to skill communal subsistence farmers.

Strategy to Minimize Plant Accumulation of Contaminants of Emerging Concern: Alternation between Treated Wastewater and Freshwater Irrigation

Treated wastewater (TWW) is increasingly used for agricultural irrigation in arid and semiarid areas, but it can introduce contaminants of emerging concern (CECs) into the food chain, posing a potential risk to human health. While many studies have shown that plants can accumulate some CECs, so far little effort has been made to explore mitigation strategies. This study tested the concept of alternating between TWW with conventional freshwater for irrigation to minimize CEC accumulation in plants. Tomato and lettuce seedlings were first cultivated in CEC-containing hydroponic solutions for 3 weeks, and then in CEC-free media for another 3 weeks. The plant tissues contained elevated concentrations of perfluorobutanesulfonate, perfluorobutanoic acid, perfluorohexanoic acid, carbamazepine, and fluoxetine ranging from 42.1 to 2724.2 ng/g (dry weight). However, after being transferred to CEC-free media, most CEC levels decreased by over 75%, attributed to plant metabolism, growth dilution and back release to culture media. This proof-of-concept study suggested that using TWW during the early part of the growing season may effectively minimize CEC accumulation. Such hybrid irrigation schemes have a great prospect for expanding the safe reuse of TWW and other lower-quality water sources in agriculture and should be further evaluated under field conditions.

Physiological responses of three field-grown species (Ceratonia siliqua, Eucalyptus camaldulensis, and Moringa oleifera) to water deficits in a Mediterranean semi-arid climate

Reforestation of degraded drylands calls for the selection of species with the capacity to withstand water scarcity. In this current study we have assessed, the physiological responses of three field-grown species (Ceratonia siliqua, Eucalyptus camaldulensis and Moringa oleifera) to water deficits in semi-arid regions in order to suggest a potential species for rehabilitation programs. The physiological behavior of the given species was studied in three irrigation schemes: subsurface drip irrigation (applied weekly), tank irrigation (applied monthly), and unirrigated plants. In a stressed state, an assessment of relative water content (RWC), water potential (pre-dawn water potential PWP and midday water potential MWP) and stomatal conductance revealed three contrasting physiological responses. First, C. siliqua stomata remained open with a high RWC at low water potentials. Consequently, this species tolerated water deficits by decreasing its leaf water potential, primarily associated with osmotic adjustment. On the other hand, E. camaldulensis was found to be a drought-avoider species, mutated to a water-saving strategy by complete stomatal closure. Finally, for the extreme case, M. oleifera showed leaf shedding under water deficit conditions. These different physiological responses allowed these species to survive water deficits, and consequently, could be considered suitable candidates for rehabilitating degraded semi-arid areas.

Evaluating the Combined Effects of Water and Fertilizer Coupling Schemes on Pear Vegetative Growth and Quality in North China

Unreasonable fertilizer and irrigation applications and dosages in orchards in northern China result in poor vegetative growth and fruit quality. To reveal the combined effect of water and fertilizer coupling on vegetative growth and fruit quality, this study used pear as a field experiment material, considering: (1) irrigation lower limits (55%, 65%, 75%θf, θf is field capacity) and (2) nitrogen fertilizer application (162, 324, 486 kg·ha−1). Nine coupling schemes and a control treatment (C) were set up in the orthogonal combination. The results showed that, under the higher irrigation rate and nitrogen dose, the spring shoot length, base diameter, and leaves relative chlorophyll content values were increased by 36.77%, 31.86% and 12.91%, respectively. The response of each coupling scheme was different. However, selected water and nitrogen coupling schemes improved the fruit quality. The evaluation results indicated that medium irrigation and high fertilizer scheme were optimal. In conclusion, integrating the vegetative growth and fruit quality, it is recommended that the water and fertilizer coupling scheme for pear in the northern China is as follows: a lower irrigation limit of 65%θf and a nitrogen fertilizer amount of 486.00 kg·ha−1.

Small-Scale Farmers' Vulnerability to Biophysical and Socio-Economic Risks in Semi-Arid Lowlands of Mwanga District, Kilimanjaro Region, Tanzania.

Agricultural production systems in semi-arid areas are vulnerable to a myriad of risks. Using a systems approach of risk framework and a mixed-methods research design, this paper sought to explore selected biophysical and socio-economic risks that contributed to vulnerability of agricultural production systems in the semi-arid lowlands of Mwanga District, Kilimanjaro Region, Tanzania. Despite the lack of statistically significant relationships between amounts of rainfall and crop production in the district, 30 focus group participants perceived that spatial and temporal changes of rainfall distribution as coupled with increased crop pest/disease outbreaks and soil loss contributed to vulnerability of agricultural production systems in terms of frequent crop failure and famine particularly amongst farmers who practised rain-fed farming in the semi-arid lowlands. Furthermore, participants perceived that crop production and yields were negatively influenced by poor marketing and institutional structures and that crop production and yields were negatively influenced by farmers' poor access to appropriate technologies including seeds, fertilizers, agrochemicals, agricultural machinery and infrastructure including modern irrigation schemes and all-weather roads. By way of conclusion, reduced vulnerability of agricultural production systems calls for integrated enhancement of farmers' capacity in addressing the biophysical, agro-industrial and institutional risks.

Dynamic Optimization of Greenhouse Tomato Irrigation Schedule Based on Water, Fertilizer and Air Coupled Production Function

A vegetable water production function has been one of the most significant parameters to improve the use efficiency and economic benefit of agricultural water in the greenhouse. Meanwhile, aerated irrigation unlocks the high yield potential for greenhouse crop production. Thus, water, fertilizer and air coupled production function is proposed for the optimization of the irrigation scheme during the greenhouse tomato growth period. Two seasons of greenhouse tomato experiments were conducted under aerated subsurface drip irrigation (ASDI). There were three nitrogen application rates (N1, 120 kg ha−1; N2, 180 kg ha−1; N3, 240 kg ha−1) and three aeration rates with dissolved oxygen (DO) in irrigation water (A2, 15 mg L−1; A3, 40 mg L−1 and A1, 5 mg L−1 in the non-aeration treatment) in the first crop season, while three irrigation rates of soil moisture content (W1, 50–60% field capacity; W2, 60–70% field capacity; W3, 70–80% field capacity) and two aeration rates with DO in irrigation water (25 mg L−1 and 5 mg L−1) in the second crop season. The potential yield function of tomato was constructed, and the water sensitivity index was resolved. The production function of greenhouse tomato under water, fertilizer, and air coupled irrigation was established based on the Jensen function. The water allocation scheme under multiple irrigation quotas was optimized by the dynamic programming (DP) method. The results showed that with the elapse of crop growth stages, the cumulative curve of the water sensitivity index showed an S-shaped curve, which first rose slowly and then fast, and eventually tended to be stable. The optimized irrigation increased the yield by 4.25% averagely compared with the irrigation method of fixed moisture content interval, while the crop yield in the optimized ASDI increased by 26.13% compared with non-aeration treatment. In summary, the optimal combination was the aeration rate DO of 24.55mg L−1 in irrigation water and nitrogen application rate of 281.43 kg ha−1, and the irrigation quota of 420 mm. The net yield increased by 11,012 USD ha−1 in a single crop season when compared with the non-aeration treatment. The results would provide a reference method for the optimization of technical parameters of water—fertilizer—air coupled irrigation.

Usutu virus: a Flavivirus on the rise amid COVID-19 and monkeypox

Usutu virus: a Flavivirus on the rise amid COVID-19 and monkeypox

Prevalence and distribution of urinary schistosomiasis among senior primary school pupils of Siphofaneni area in the low veld of Eswatini: A cross-sectional study.

A cross-sectional survey of Schistosoma haematobium prevalence was conducted among senior primary school pupils of Siphofaneni area, Eswatini. This area is devoid of potable water, with a newly constructed Lubovane dam and an LUSIP irrigation scheme. The objective of the study was to investigate the distribution of urinary schistosomiasis among Siphofaneni senior primary school pupils. Using simple random sampling, 200 partcipants were enroled from four of six schools in the area. Ten millimetres (10 ml) of urine samples were obtained from each participant and examined for S. haematobium eggs. The intensity of the infection was estimated by calculating the total number of S. haematobium eggs present in 10 ml urine. Out of 200 participants, 45% (n = 91) were males, and 55% (n = 109) were females. The mean age for participants was 13 years, and almost half (47%, n = 94) were in Grade 5. Overall, the prevalence of S. haematobium infection was 16% (32/200). More than half (59%, 19/32) of the Schistosomiasis cases were from females. Positive and significant associations were observed between the number of eggs (χ2=170.9) and the presence of red blood cells (χ2=49.2) at p = 0.001. In conclusion, the prevalence of Schistosomiasis is high among pupils enrolled in Siphofaneni area primary schools that needs comprehensive treatment and education to prevent from S. haematobium infection.

Modeling of land suitability for surface irrigation using analytical hierarchy process method in Belessa Districts, northwestern Ethiopia

The objective of this paper was to determine whether the land in Belessa is suitable for surface irrigation. For this, a GIS-based Analytical hierarchy process method was applied. Eight factors/parameters such as soil type, soil depth, soil texture, soil drainage, slope, distance from a water supply, and land cover were used to evaluate the suitability of the area for surface irrigation. The weight of each parameter was calculated using an 8 × 8 pairwise comparison matrix. Then, the land suitability map for surface irrigation was produced by adding weighted parameters using the weighted overlay method under ArcGIS 10.3 software. The land suitability map was divided into four categories: highly suitable (S1), moderately suitable (S2), marginally suitable (S3), and unsuitable (S4 or N1). The results show that 12.2% of the study area is not suitable (S4 or N1) for surface irrigation, whereas 13.9% of the study area is highly suitable (S1) for surface irrigation. Marginally (S3) and moderately suitable (S2) classes covered 26.9%, and 46.9% of the study area, respectively. The accuracy of the model was evaluated by overlaying preexisted irrigation scheme in the study area, which falls under highly and moderately suitable area, confirms that the model is accurate. Therefore, this result will be important to increase crop production in the study area, by implement surface irrigation in highly and moderately suitable lands.

APPLICATION OF MULTITEMPORAL LANDSAT DATA IN MAPPING OF SALINE SOIL IN KANO RIVER IRRIGATION SCHEME (KRIS)

Soil salinization is becoming a more serious issue threatening agricultural production and the sustainable use of land resources. Crop roots are unable to absorb water from the soil when exposed to saline conditions. This study explored the potential of Landsat imagery in detecting and mapping saline soil in the Kano River Irrigation Scheme (KRIS). Samples of soil were collected from thirty-nine (39) sectors of the KRIS for ground truthing on 20th – 25th April, 2020. Electrical Conductivity (EC) of field samples were correlated with band values of satellite images and salinity indices in order to determine their relationship and assess their effectiveness in predicting soil salinity. Using a geospatial approach, the data was analyzed and maps of salt-affected areas were generated. ArcGIS 10.6 was used as the primary package for modeling and running functions. The result has shown that the EC values over the entire study area are greater than 1.3 dS/m. However, the mean value of EC is approximately 1.91 dS/m. The implication is that, most of the vegetables such as Onion, Carrot, and Beans grown in the KRIS will experience yield reduction without appropriate management practice as their threshold value has been exceeded.

Together Strong or Falling Apart? Coping with COVID-19 in Smallholder Irrigated Agriculture

Coping, surviving and living with different kinds of crisis is a recurrent challenge to those governing groundwater as a common resource. In this paper, we mobilise ideas about the functioning of the state and of processes of bricolage to explain the functioning of institutions governing groundwater during the Covid-19 pandemic. Drawing on empirical material from one irrigation scheme in Zimbabwe we argue that such institutions show signs both of transformation and degeneration over the course of the Covid-19 crisis. Our analysis shows the emergence of temporary and innovative ways of collectively organising around groundwater which ensure improved access to water during the pandemic. Such new ways of doing things draw on different sources of authority and legitimacy in shaping governance arrangements. However, as the pandemic situation becomes the ‘new normal’, collective arrangements degenerate into a pre-Covid-19 state, or worse, further restricting access and representation for some people.

Small-scale irrigation (SSI) farming as a climate-smart agriculture (CSA) practice and its influence on livelihood improvement in Offa District, Southern Ethiopia

Small-scale irrigated farming has been offered as a climate-smart agriculture (CSA) technology to boost production and diversify livelihood scenarios as an option to mitigate climate change. This study was to analyse factors that influence smallholder farmers' decisions to adopt small-scale irrigation (SSI) as CSA and to assess the influence of adoption on livelihood improvement. To obtain relevant data, the study employed a mixed research methodology that combines an explanatory research design with a qualitative approach. A total of 134 respondents were selected for the study's sample size. A mixed research methodology was used in this study to acquire pertinent data, which incorporated an explanatory research design and a qualitative approach. In the study area, 37.3% participated in small-scale irrigation, while 62.7% did not. The descriptive statistics result showed that, household socio-demographic factors; household socio-economic factors, and household institutional factors had significantly and statistically affect the adoption SSI. The Logit regression model results revealed that households; who owned more land holding size, access to credit services, get agricultural extension service, who near to the district market, who have middle age of HH, who Sex of HHH, who nearest farm sight, have TLU, have farming experience, have access to irrigation, and have good health status of the HHH were more likely to benefit from the use of small scale irrigation. The average annual gross income earned by participant and non-participant households from various crops in the three schemes was 370,190 and 83,983 ETB, respectively. As a result, participation in small-scale irrigation has a positive effect on the majority of household livelihood diversification, and expanding irrigation schemes improves rural farm households' livelihoods. As a result, policymakers and other stakeholders should prioritize small-scale irrigation technologies as CSA to improve rural household livelihoods.

Sustainable Environmental Economics in Farmers’ Production Factors via Irrigation Resources Utilization Using Technical Efficiency and Allocative Efficiency

This study reports the results of farmers’ production via irrigation resources utilization and efficiency parameters of technical efficiency and allocative efficiency by way of sustainable environmental economics. The hypothesis is that factors of farmers’ production affect technical efficiency and allocative efficiency in the irrigation scheme as sustainable environmental economics. Data from cross section and panel data were used and then the productivity parameters measurement of the production function are outlined in two scenarios: first, the data report that the parameters such as output elasticity determine factors of inefficiency and technical efficiency. Second, it presents the scores for the allocative efficiency to explain whether production factors (resources) are optimally, under- or over-allocated by farmers in the irrigation systems under environmental sustainability. This paper presents the productivity and efficiency parameters estimated using stochastic frontier analysis for the translog production function, which was estimated by the MLE method, and the allocative efficiency for the factor inputs allocation in the irrigation systems estimated by ordinary least square for the Cobb-Douglas production function. This study concludes that collective farmers lead into technical inefficiency and over use of factors of production.

Analysis of Rice Marketing Channels Choices in Mwea Irrigation Scheme, Kirinyaga County, Kenya

The National Rice Development Strategy in (Kenya vision 2030) aims to improve food security, rural employment, and income for smallholder farmers in the Mwea irrigation scheme (MIS) through planned and intentional efforts. A study was conducted to identify major influences in choosing market avenues among rice farmers. The study used a sample size of 384 small-scale rice farmers to analyze the different rice marketing channels used in MIS, and to understand the factors that influence farmers’ choices of marketing channels. A pretested semi-structured questionnaire was used for data collection. Descriptive statistics were used to characterize the marketing channels, multinomial logit model was used to evaluate channel choices. The marketing channels were Channel 1: Farmer-Consumer (0.3%); Channel 2: Farmer-Brokers-Millers-Consumer (51.1%); Channel 3: Farmer-Brokers-Millers- Retailer-Consumer (42.3%); Channel 4: Farmer- Millers-Retailer-Consumer (62.72%) and Channel 5: Farmer- Millers- Wholesaler-Retailer-Consumer (37.28%). The most profitable channel was direct sales to consumers, which accounted for only 0.3% of total rice production in MIS. The study also found that factors such as education level, participation in marketing groups, distance to market, and age of the household head significantly influenced farmers’ choice of marketing channels. The study is critical in enriching literature on rice agricultural supply chains in Kenya. The study recommends policy considerations to protect small-scale farmers from exploitative brokers and suggests registering brokers to monitor their activities and set standards for fair practices, with the goal of regulating their activities to prevent exploitation of small-scale farmers in rice marketing.

Impact of climate and irrigation practices on hydrological aspects of Bundala wetlands in Sri Lanka

AbstractBundala wetlands are the first to be declared a Ramsar wetland reserve in Sri Lanka. Two wetlands of this complex have transformed from seasonally inundated saline areas into permanent freshwater ecosystems, resulting in spatial and temporal changes that presumably have favoured plant invasions. We hypothesized that climate/rainfall changes and irrigation practices would be the most potential drivers of this change, and the objective of this research is to empirically determine the influence of rainfall and irrigation practices in the catchment on inundation pattern and plant nutrient availability that could potentially change ecology of these wetlands. Monthly rainfall data for the Bundala area (1988–2017) from Sri Lanka's meteorological department were analysed by parametric and nonparametric statistical methods, and a statistically significant change in rainfall was not discernible, confirming climate change is unlikely to be a driver to increase the lagoon water level. Irrigation data analysis revealed that these wetlands receive nearly 1.28 × 107 m3 of irrigation drainage annually from an irrigation scheme in the immediate catchment, which has resulted in decreased salinity, while inundation and plant nutrient content increased, changing the wetlands' ecology and socioeconomic status of the dependent rural communities.

The Determinants of Smallholder Farmers on the Functionality of Plant Health Clinics in the Vhembe District, South Africa

A plant health clinic is a system in which under-resourced and smallholder farmers can access basic services of plant healthcare from a plant clinic in relation to infected or symptomatic plants and plant products for pest diagnostic and identification purposes. The factors that influence smallholder farmers’ awareness and accessibility to plant health clinics in the Vhembe District Municipality of Limpopo Province, South Africa were examined in this study. The study also identified the constraints of the plant clinics that prevent their effective utilization. Three-hundred and twenty smallholder farmers (n = 320) from the population of 1600 were interviewed through a semi-structured questionnaire. A multistage random sampling technique was employed to select the 320 smallholder farmers from 8 irrigation schemes in the study area. To ensure representation, all categories of smallholder farmers were included in the study. Descriptive statistics such as frequency and percentages and Logit regression model were employed for the data analyses. The results revealed that there is a statistically significant and positive relation between communication channels and plant clinics awareness and accessibility among smallholder farmers. The distance to plant clinics has a negative influence on the accessibility of plant clinics among the farmers; however, the accessibility of plant clinic improves when visits by extension officers or plant doctors to farmers increase. The study pointed out some challenges affecting the functionality of plant clinics, which could be resolved through an efficient and effective plant clinic framework that involves major role players. An efficient and effective plant clinic framework was therefore developed by the study to improve its usefulness for diagnosing plant pest symptoms and diseases. The study concluded that plant clinic framework was important and should be considered and adopted by policy makers within the government, research institutes, and other NGOs.

Estimating the Effects of Deficit Irrigation on Water Absorption and Utilization of Tomatoes Grown in Greenhouse with Hydrus-1D Model

Quantitative analysis of tomato root water uptake and soil water utilization in the root zone under deficit irrigation is an important tool to improve agricultural water utilization efficiency. In this study, three different deficit irrigation levels were set at the flowering and fruit development stage (Stage I) and the fruit-ripening stage (Stage II), respectively. The Hydrus-1D model and field data were used to analyze the effects of deficit irrigation on tomato root growth, soil water uptake and utilization in the root zone. The results showed that deficit irrigation could reduce the total root length density of water-absorbed roots but increase the water-absorbed root length density of the underlying soil (30–60 cm). Moderate and severe water deficits at Stage II increased the water-absorbed root length density of the underlying soil by 0.10–6.26% and 2.12–11.71% compared with a mild water deficit. Considering tomato root growth, the Hydrus-1D model can improve the accuracy of soil moisture simulation. The main water absorption zone of tomato roots was 0–30 cm. Compared with full irrigation, the ratio of water absorption by the underlying root system (30–60 cm) to the total water absorption of the profile (0–60 cm) increased by 2.16–2.82% and 5.34–6.34% due to mild and moderate water deficits at Stage I. At Stage I and Stage II, a water deficit could reduce soil evaporation. T3 had the highest water use efficiency in two years, which was 24.07% (T9) and 20.47% (T8) higher than the lowest value, respectively. The optimal deficit irrigation scheme under this experiment condition is as follows: the soil water content was 70–90% θf (field capacity) at Stage I and was 40–60% θf at Stage II (T3).

Responses of the Leaf Water Physiology and Yield of Grapevine via Different Irrigation Strategies in Extremely Arid Areas

The contradiction between water supply and demand has become increasingly prominent due to the large agricultural water consumption and low irrigation water use efficiency (IWUE) in the extremely arid area of Xinjiang, which needs to be solved by efficient irrigation. In this study, the effects of different irrigation levels (the lower and upper limits of irrigation (LULI) were 50–80%, 60–90%, and 70–100% of the field capacity (FC), respectively) under two irrigation methods (root zone irrigation (RZI) and furrow irrigation (FI)) on the photosynthetic physiology and yield of grape were analyzed to explore suitable irrigation schemes in extremely arid areas. The results show that the diurnal variation curve of the net photosynthetic rate (Pn) of grape leaves in the extreme arid region was not sensitive to the response of irrigation methods. However, RZI could improve the apparent quantum efficiency and maximum photosynthetic rate by 60.00% and 31.25%, respectively, reduce the light compensation point by 17.91%, and alleviate the photosynthetic lunch break phenomenon. Under FI, the physiological indexes of leaves increased with the increase in the LULI, while the Pn and SPAD values were the largest under RZI when the LULI was 60–90% of FC. The daily average Pn value of T2 in 2021 and 2022 ranged from 12.93 to 17.77 μmol·m−2·s−1. Compared with FI, RZI significantly improved the leaf water potential, Pn, and SPAD values by increasing the soil water content (SWC) of the 40–80 cm soil layer by 5.04–8.80%, which increased the yield by 6.86–18.67%. The results show that the yield and water use efficiency reached the peak when the LULI was 60–90% of FC under RZI, which could provide theoretical support for efficient irrigation of vineyards in extremely arid areas.

Spatial Downscaling of GRACE Data Based on XGBoost Model for Improved Understanding of Hydrological Droughts in the Indus Basin Irrigation System (IBIS)

Climate change may cause severe hydrological droughts, leading to water shortages which will require to be assessed using high-resolution data. Gravity Recovery and Climate Experiment (GRACE) satellite Terrestrial Water Storage (TWSA) estimates offer a promising solution to monitor hydrological drought, but its coarse resolution (1°) limits its applications to small regions of the Indus Basin Irrigation System (IBIS). Here we employed machine learning models such as Extreme Gradient Boosting (XGBoost) and Artificial Neural Network (ANN) to downscale GRACE TWSA from 1° to 0.25°. The findings revealed that the XGBoost model outperformed the ANN model with Nash Sutcliff Efficiency (NSE) (0.99), Pearson correlation (R) (0.99), Root Mean Square Error (RMSE) (5.22 mm), and Mean Absolute Error (MAE) (2.75 mm) between the predicted and GRACE-derived TWSA. Further, Water Storage Deficit Index (WSDI) and WSD (Water Storage Deficit) were used to determine the severity and episodes of droughts, respectively. The results of WSDI exhibited a strong agreement when compared with the Standardized Precipitation Evapotranspiration Index (SPEI) at different time scales (1-, 3-, and 6-months) and self-calibrated Palmer Drought Severity Index (sc-PDSI). Moreover, the IBIS had experienced increasing drought episodes, e.g., eight drought episodes were detected within the years 2010 and 2016 with WSDI of −1.20 and −1.28 and total WSD of −496.99 mm and −734.01 mm, respectively. The Partial Least Square Regression (PLSR) model between WSDI and climatic variables indicated that potential evaporation had the largest influence on drought after precipitation. The findings of this study will be helpful for drought-related decision-making in IBIS.