Irrigation Water Demand Research Articles

Climate resilience and the human-water dynamics. The case of tomato production in Morocco

In Morocco, droughts are an increasing threat affecting water availability, agricultural production and producers' livelihoods. Moreover, water demand for irrigation has led to overexploitation of the groundwater table causing significant natural resource management challenges. The combination of groundwater changes and increasing drought risk raises concerns about the ability of agricultural producers to be resilient against drought. In this study, we describe the interactions of environmental and socioeconomic processes which influence farmers' livelihoods involved in tomato production in Morocco. Building on system dynamics modelling tools, we aim to improve the understanding of the long-term dynamic behavior of water management and to explore plausible policy scenarios necessary for sustainable and resilient water resource management and agricultural development. Our results show that tomato production is not yet severely impacted by droughts. However, droughts are accelerating the process of groundwater depletion, impacting farmers' livelihoods, by decreasing crop productivity and reducing farmer's revenue over a longer time period, especially since tomatoes are a high-value crop. Therefore, integrated and effective policies are presented as a set of measures for a systemic enhancement of resilience. We conclude that a more radical approach toward water resource conservation and upholding the most vulnerable producers has to be adopted in order to enhance a sustainable and inclusive resilience of the tomato production in Morocco.

Satellite data-driven multi-objective simulation-optimization modeling for water-environment-agriculture nexus in an arid endorheic lake basin

In the arid endorheic lake basin with highly developed agriculture, water scarcity drives the nexus of water-environment-agriculture (WEA) while potential evapotranspiration (ETp) is a critical element linking basin-scale irrigation water demand and agro-economic development. The study proposes a satellite remote sensing data-driven multi-objective simulation-optimization (SO) framework to implement the basin-scale WEA nexus management. The hydrological model (MODFLOW-NWT) combined with the MODIS (Moderate Resolution Imaging Spectroradiometer) based ETp estimation with a 500-m spatial resolution simulates the monthly surface water (SW) and groundwater (GW) irrigation practices. Then, the multi-objective evolutionary algorithm (ε-MOMA) is applied to solve management model which includes maximization of agro-economic benefit and environmental flow and minimization of environmental risk of total nitrogen loading subject to irrigation water demand, land availability and food supply. The SO framework is validated in an arid endorheic lake basin with intensive agricultural irrigation in northwestern China. The four-dimensional Pareto-optimal solutions are achieved to optimize crop planting structure and irrigation water allocation in order to avoid cognitive myopia triggered by low-dimensional or single objective optimization. The results highlight the trade-off among the high value crop planting, SW-GW irrigation and environmental flows, and indicating that lowering nitrogen loading is more sensitive to agro-economic benefit. Historical maximum and minimum ETp scenarios are tailored to quantify the impact of ETp change on WEA nexus management. Results show the increasing ETp has a great negative effect on the environmental flow objectives. Therefore, how multi-sectoral interests change depending on the basin-wide development goals may be difficult to regulate due to complex WEA nexus and associated deep uncertainty in the future.

Salinity impacts on irrigation water-scarcity in food bowl regions of the US and Australia

Irrigation water use and crop production may be severely limited by both water shortages and increased salinity levels. However, impacts of crop-specific salinity limitations on irrigation water scarcity are largely unknown. We develop a salinity-inclusive water scarcity framework for the irrigation sector, accounting for crop-specific irrigation water demands and salinity tolerance levels and apply it to 29 sub-basins within two food bowl regions; the Central Valley (CV) (California) and the Murray–Darling basin (MDB) (Australia). Our results show that severe water scarcity (levels >0.4) occurs in 23% and 66% of all instances (from >17 000 monthly crop-specific estimates) for the CV and MDB, respectively. The highest water scarcity levels for both regions occurred during their summer seasons. Including salinity and crop-specific salinity tolerance levels further increased water scarcity levels, compared to estimations based on water quantity only, particularly at local sub-basin scales. We further investigate the potential of alleviating water scarcity through diluting surface water with lower saline groundwater resources, at instances where crop salinity tolerance levels are exceeded (conjunctive water use). Results from the CV highlights that conjunctive water use can reduce severe water scarcity levels by up to 67% (from 946 monthly instances where surface water salinity tolerance levels were exceeded). However, groundwater dilution requirements frequently exceed renewable groundwater rates, posing additional risks for groundwater depletion in several sub-basins. By capturing the dynamics of both crops, salinity and conjunctive water use, our framework can support local-regional agricultural and water management impacts, on water scarcity levels.

Irrigation water demand and elasticities: a case study of the High Plains aquifer

The agriculture of the Texas High Plains (THP) region is primarily dependent on groundwater irrigation. Changing weather patterns along with competing demands for water resources and other anthropogenic effects have dramatically increased withdrawals from the Ogallala aquifer. In addition to on-farm changes, policy tools based on off-farm mechanisms are equally indispensable in addressing sustainable groundwater use in the THP. One such policy tool is water pricing using estimates of price elasticity of irrigation water demand. This paper estimates the elasticity of irrigation water demand in the THP and assesses the influence of water price on major inputs used in dominant irrigated crops such as corn and cotton. Using the translog profit function on an annual county-level dataset of THP crop production, spanning 23 years (1998–2020), we find that irrigation water demand is price elastic for cotton (η = – 1.58) but inelastic for corn (η = – 0.81). Our findings suggest that a non-uniform pricing policy could be a useful tool to promote the efficient use of groundwater for irrigation.

Assessment of Crop Water Demand and Irrigation Water Supply in a Run-off-the-river Based Canal System

Proper assessment of irrigation water need for a canal command is required for long term planning and management of water resources. The present study was carried out in the Phulnakhara distributary command of the Puri main canal system distributed in Cuttack and Khurda districts of Odisha. During Kharif season, the Phulnakhara distributary command receives more than the required amount of irrigation water. However, during Rabi season, the canal does not flow at its full supply level as a result of which the total irrigation demand of the canal command area is not met leading to lower cropping intensity and poor crop productivity. The year-wise highest irrigation water demand in Kharif season was found to be 48646195 m3 during 2015-16 and the lowest was 22291100 m3 in 2017-18. Whereas the highest Kharif irrigation supply at the head regulator was 43402176 m3 during 2015-16 and the lowest was 29831328 m3 during 2013-14. The highest Rabi irrigation water demand was found to be 21700766 m3 during 2008-09 and the lowest was 9570257 m3 in 2017-18. Whereas the highest Rabi irrigation supply at head regulator was 26379648 m3 during 2008-09 and the lowest was 615168 m3 during 2009-10. As evident, there is a mismatch between the supply and demand in both the seasons and it is more prominent in the Rabi season. In order to bridge this gap, conjunctive use of canal water with groundwater is found to be a promising solution.

County-Level Irrigation Water Demand Estimation Using Machine Learning: Case Study of California

Irrigated agriculture is the largest consumer of freshwater globally. Despite the clarity of influential factors and deriving forces, estimation of the volumetric irrigation demand using biophysical models is prohibitively difficult. Data-driven models have proven their ability to predict geophysical and hydrological phenomena with only a handful of influential input variables; however, the lack of reliable input data in most agricultural regions of the world hinders the effectiveness of these approaches. Attempting to estimate the irrigation water demand, we first analyze the correlation of potential influencing variables with irrigation water. We develop machine learning models to predict California’s annual, county-level irrigation water demand based on the statistical analysis findings over an 18-year time span. Input variables are different combinations of deriving meteorological forces, geographical characteristics, cropped area, and crop category. After testing various regression machine learning approaches, the result shows that Gaussian process regression produces the best results. Our findings suggest that irrigated cropped area, air temperature, and vapor pressure deficit are the most significant variables in predicting irrigation water demand. This research also shows that Gaussian process regression can predict irrigation water demand with high accuracy (R2 higher than 0.97 and RMSE as low as 0.06 km3) with different input variable combinations. An accurate estimation of irrigation water use of various crop categories and areas can assist decision-making processes and improve water management strategies. The proposed model can help water policy makers evaluate climatological and agricultural scenarios and hence be used as a decision support tool for agricultural water management at a regional scale.

Evaluating a reservoir parametrization in the vector-based global routing model mizuRoute (v2.0.1) for Earth system model coupling

Abstract. Human-controlled reservoirs have a large influence on the global water cycle. While global hydrological models use generic parameterizations to model dam operations, the representation of reservoir regulation is still lacking in many Earth system models. Here we implement and evaluate a widely used reservoir parametrization in the global river-routing model mizuRoute, which operates on a vector-based river network resolving individual lakes and reservoirs and is currently being coupled to an Earth system model. We develop an approach to determine the downstream area over which to aggregate irrigation water demand per reservoir. The implementation of managed reservoirs is evaluated by comparing them to simulations ignoring inland waters and simulations with reservoirs represented as natural lakes using (i) local simulations for 26 individual reservoirs driven by observed inflows and (ii) global-domain simulations driven by runoff from the Community Land Model. The local simulations show the clear added value of the reservoir parametrization, especially for simulating storage for large reservoirs with a multi-year storage capacity. In the global-domain application, the implementation of reservoirs shows an improvement in outflow and storage compared to the no-reservoir simulation, but a similar performance is found compared to the natural lake parametrization. The limited impact of reservoirs on skill statistics could be attributed to biases in simulated river discharge, mainly originating from biases in simulated runoff from the Community Land Model. Finally, the comparison of modelled monthly streamflow indices against observations highlights that including dam operations improves the streamflow simulation compared to ignoring lakes and reservoirs. This study overall underlines the need to further develop and test runoff simulations and water management parameterizations in order to improve the representation of anthropogenic interference of the terrestrial water cycle in Earth system models.

Historical climate change impacts on the water balance and storage capacity of agricultural reservoirs in small ungauged watersheds

Study regionAgricultural reservoirs are the principal source of irrigation supplies for sustaining rice production and play a critical role in the water resource management of South Korea. Study focusWe comprehensively evaluated the performance of 400 major agricultural reservoirs, spread throughout the country, as a function of climate change during 1973–2017 considering the constituents of reservoir water balance, such as watershed runoff, irrigation water demand, and evaporation loss. New hydrological insightsBased on the trend analysis during the 45-year study period, the reservoir inflows remained higher than the irrigation water demands because of the gradually increasing annual rainfall. Most reservoirs had enough storage capacities; their resilience gradually declined particularly during the last 15 years. The northern and northeastern region reservoirs had acceptable resilience whereas the reservoirs in the western and southwestern inland and coastal regions showed insufficient resilience. Reservoirs received sufficient inflows but the residence time of the excess inflow has to be increased to suffice the peak irrigation demands in the coming cropping season. Study outcomes could help prioritize the reservoirs requiring immediate rehabilitation located in the central and southwest regions with high failure risks. Results suggested that a reservoir with a watershed-irrigated area ratio > 5 would have a better chance of coping with future climate change threats.

Impact of drought and salinity on olive potential yield, oil and fruit qualities (cv. Chemlali) in an arid climate

The increase water demand for irrigation is leading to the use of low-quality water resources. The combined impact of drought and salinity on olive production sustainability, yield quality, growth, soil salinity and soil water conditions in arid areas has been little investigated. This study’s purpose was conducted to investigate the effects of the monitoring of saline water irrigation on soil properties and olive trees (cv. Chemlali) grown in an arid region of Tunisia (Sfax), on the potential yield, growth and quality of the resultant virgin olive oil in comparison to Rain-fed conditions. It is also intended to compare olive productive performance during a severe drought with, and without, irrigation and to assess recovering capacities after long driest period. Three irrigation levels were considered: (i) Full irrigation (100%ETc) with saline water 7.5 dS m-1 (FI); (ii) Full irrigation with same amount of water than the FI applied with tap water 2.46 dS m-1 (TW); and (iii) Rain-fed conditions (Dry). The results have showed that irrigation with saline water maintained the soils permeability, induced the distribution of salts outside the root zone. Additionally, it has maintained an adequate hydration of the rhizosphere through continuous and efficient leaching of salts to deep horizons. After drought period, the increase of the yield of rain-fed trees indicated 50% of recovery as compared to saline water. Irrigation with saline water reduced this gap due to drought impact. But it was 50% under that tap water; while reduction was 15% as a reduction capacity of potential yield. Hence, drought and salt stress alter the olive tree capacity and potential yield in an irreversible way if their severity is very intense. As salinity increased, there was a desirable sink in measured total phenols and flavonoids levels and a rise of oleic and linoleic acids as compared to rainfed conditions. For the triglycerides composition, triolein (OOO) was present in very large quantity in three oils, with a high content for FI (23.94%). Saline water treatment did not affect free acidity, peroxide value, K232, K270, chlorophyll, carotenoids, in contrast to Rain-fed treatment which was decreased. Olive trees permanently lost less than half of their potential yield during drought without irrigation. Irrigation with saline water seems to ensure sustainable monitoring olive yield and oil quality.

South Asian agriculture increasingly dependent on meltwater and groundwater

Irrigated agriculture in South Asia depends on meltwater, monsoon rains and groundwater. Climate change alters the hydrology and causes shifts in the timing, composition and magnitude of these sources of water supply. Simultaneously, socio-economic growth increases water demand. Here we use a high-resolution cryosphere–hydrology–crop model forced with an ensemble of climate and socio-economic projections to assess how the sources of irrigation water supply may shift during the twenty-first century. We find increases in the importance of meltwater and groundwater for irrigated agriculture. An earlier melt peak increases meltwater withdrawal at the onset of the cropping season in May and June in the Indus, whereas increasing peak irrigation water demand during July and August aggravates non-renewable groundwater pumping in the Indus and Ganges despite runoff increases. Increasing inter-annual variability in rainfall runoff increases the need for meltwater and groundwater to complement rainfall runoff during future dry years.

Irrigation water demand management with emphasis on pricing policy

Abstract Serious constraints in increasing water supply have led countries around the world to seek solutions for managing water demand. Proper pricing of water is one of the foremost water demand management policies which can lead to the optimal water use. On the flip side, the quality of agricultural water is declining due to the uncontrolled abstraction of groundwater. In this regard, the present study aims to determine the economic value of different qualities of water throughout pistachio-growing regions of the Rafsanjan-Anar plain in Iran. Results reveal that the economic value and price elasticity of water demand differ among different groups. Freshwater, moderately saline water and highly saline water have the highest to lowest elasticity and shadow price, respectively. Additionally, comparison of the gross margin, which represents the profit from each activity, in two conditions including the unsustainable status quo and sustainable conditions intended by the Ministry of Energy, shows that although water use has declined by 50%, the gross margin has decreased by only 36%. This implies it is feasible to reduce water use in pistachio orchards by water re-allocation with a minimum decline in profit, which will both reduce water use and ensure high economic benefits for farmers.

Integrated water management under climate change through the application of the WEAP model in a Mediterranean arid region

Abstract This research aims at establishing an integrated modelling framework to assess the impact of climate change on water supply and demand across an arid area in the western Haouz plain in Morocco. Five general circulation models (GCMs) are used to evaluate the availability of future water resources under Representative Concentration Pathways (RCP4.5 and RCP8.5 emission scenarios). The projected crop water demand and irrigation water demand were analysed using the Aquacrop software, taking into account the impact of climate change on both reference evapotranspiration and crop cycle lengths. The future water balance is simulated by means of the Water Evaluation And Planning (WEAP) tool, including several socio-economic and land use scenarios under RCP4.5 and RCP8.5 scenarios. The results reveal an important decrease in net precipitation with an average of −36.2% and −50.5% under RCP4.5 and RCP8.5 scenarios, respectively. In terms of water balance, the ‘business as usual’ scenario would lead to an increasing unmet water demand of about +22% in the 2050 horizon and to an increased depletion of the water table that could reach 2 m/year. Changing water management and use practices remains the only solution to ensure sustainable water use and deal with the projected water scarcity.

An atmospheric and soil thermal-based wheat crop coefficient method using additive crop growth models

Accurate crop evapotranspiration simulation is vital for reasonable irrigation planning. The two-step method for crop evapotranspiration estimation has been widely used for irrigation water demand management. However, in the two-step method, the crop coefficient (Kc) is typically taken as a constant in crop growth stages, which may result in a certain error in evapotranspiration estimation. It is of significance to estimate Kc accurately for effective water resources management. Based on three-year lysimeter experimental data collected from the Wudaogou Station for Hydrology and Water Resources, this study proposes a thermal-based Kc method for actual crop evapotranspiration estimation. The proposed thermal-based Kc method uses air temperature and soil heat flux as input variables, which could mainly characterise the thermal effect on crop growth from the atmosphere and soil. Results showed that the proposed method is effective in estimating Kc. The estimated Kc highly correlates with actual Kc values, which are derived from lysimeter observation, with correlation coefficient above 0.87 and Nash-Sutcliffe efficiency above 0.70. The proposed method could estimate Kc daily, which can be used to estimate crop evapotranspiration accurately.

Effect of Hydrocarbon Contaminated Irrigation Water On Some Selected Soil Physical and Chemical Properties of Sudan Savannah Alfisols

Due to fresh water scarcity challenges around the world, high increase in the demand for agricultural irrigation water from different sources including hydrocarbon contaminated wastewater increases. However, these wastewaters can alter soil physical and chemical properties. The aim of this study is to evaluate the impact of the hydrocarbon contaminated irrigation water on some selected soil physical and chemical properties from three phases of Sharada industrial area, Kano, Nigeria. Soil and water samples were collected from three different phases of the industrial area and analyzed using standard laboratory procedures. The hydrocarbon irrigation water quality analyses indicated that the hydrocarbon concentration in all phases was low and below irrigation reuse standard. However, the major irrigation water quality parameters; chemical oxygen demand (COD), biochemical oxygen demand (BOD), nitrate nitrogen (NO3-N), hydrogen carbonate (HCO3), ammonium-nitrogen (NH4-N), potassium (K), chlorine (Cl) and orthophosphate phosphorus (PO4-P) in all phases were all high and above irrigation reuse standard in comparison to other parameters that were compliant to standard according to literature. Pertaining the impact of the hydrocarbon irrigation water on soil properties, results revealed that soil texture was sandy loam and loamy sand, pH was neutral while bulk density (BD), electrical conductivity (EC), organic carbon (OC), total nitrogen (TN), potassium (K), sodium (Na), calcium (Ca), magnesium (Mg), cation exchange capacity (CEC) and phosphorus (P) were increased and higher compared with control soils. However, they are low in terms of concentration when compared with literature rating standard except P. Moreover, Ca, Mg, CEC and P of the soils showed significant variation statistically (P<0.05) in comparison to the remaining soil properties that recorded no significant statistical difference (P>0.05) in all phases and control soils after irrigation with the hydrocarbon wastewater. Overall, the research indicated that, the hydrocarbon wastewater was not fit for irrigation and has impacted relatively on some physical and chemical soil properties. Hence, all industries in Sharada should be directed by authorities to avoid direct discharge of their effluents without thorough quality investigation. In addition, farmers should also be educated to periodically monitor and assess the irrigation water quality of the effluents prior to application as well as incorporation of organic and inorganic amendments in the irrigated soils to uplift the concentration of the soil properties with concomitant improvement in soil fertility and quality of the study area.

Power to Hydrogen and Power to Water Using Wind Energy

The need for energy and water security on islands has led to an increase in the use of wind power. However, the intermittent nature of wind generation means it needs to be coupled with a storage system. Motivated by this, two different models of surplus energy storage systems are investigated in this paper. In both models, renewable wind energy is provided by a wind farm. In the first model, a pumped hydro storage system (PHS) is used for surplus energy storage, while in the second scenario, a hybrid pumped hydrogen storage system (HPHS) is applied, consisting of a PHS and a hydrogen storage system. The goal of this study is to compare the single and the hybrid storage system to fulfill the energy requirements of the island’s electricity load and desalination demands for domestic and irrigation water. The cost of energy (COE) is 0.287 EUR/kWh for PHS and 0.360 EUR/kWh for HPHS, while the loss of load probability (LOLP) is 22.65% for PHS and 19.47% for HPHS. Sensitivity analysis shows that wind speed is the key parameter that most affects COE, cost of water (COW) and LOLP indices, while temperature affects the results the least.

Modified Hydrological Regime on Irrigation and Water Supply in Lake Areas: A Case Study of the Yangtze River–Dongting Lake

Lake systems are of fundamental significance for the ecological environment and social development. Driven by climatic changes and human activities, the hydrological situation of rivers and lakes has been altered considerably, and it has directly affected the reliability of irrigation and water supply in lake areas. In the case of the Yangtze River–Dongting Lake area, the quasi-equilibrium of their hydrological states and water balance have been affected by the operation of the Three Gorges Project that has led to irrigation and water supply problems across the lake area. Ever since, the available water supply in the Dongting Lake area has decreased by 31.5% and 47.7% during the months of September and October, and the overall water level in the lake area has dropped by 0.8–2.0 m. The proportion of domestic and agricultural irrigation water demands to available water supply in the Dongting Lake area is very small, and the decline of water level is the main reason for the lack of water supply in Dongting Lake area, Although the total amount of water in the lake area is still above the water supply threshold, an obvious decreasing trend has been observed in the fulfillment of the demand for both irrigation and water supply in urban and rural regions. Additionally, the fulfillment of secured water supply and irrigation requirements has respectively dropped from 95% to 78% before the operation of the Three Gorges Project to 82% and 46% after it. Meanwhile, the total water shortage increased from 57.683 to 143.607 million cubic meters. By advancing or postponing impoundment schedules, the impact of the Three Gorges Reservoir on irrigation and water supply in the lake area during September and October can be alleviated, and the water supply capacity can be respectively increased by approximately 1.3% and 1.4%. The highlights of this study include the quantification of the impacts of the operation of large-scale water conservancy projects at the level at which the requirements on irrigation and water supply in the lake area are satisfied, and the prediction of the trends for future evolvement. In addition, corresponding strategies that provide a technical reference for the comprehensive regulation and control over water resources and the security of water supply in the river basin are discussed.

Training in tools to develop quantitative risk assessment of fresh produce using water reuse systems in Mediterranean production.

Water resources are increasingly coming under pressure specially around the Mediterranean area, leading to water scarcity and a deterioration in water quality. The use of treated wastewater represents an alternative source to enhance the demand for irrigation water. Water reuse in combination with the promotion of the use of water‐efficient technologies in industry and water‐saving irrigation techniques could lead to good qualitative and quantitative water status for surface and ground water bodies. Nevertheless, food‐borne outbreaks linked to fresh produce irrigated with partially or untreated wastewater caused by bacteria, parasites and enteropathogenic viruses have been widely reported. In the absence of solid scientific understanding of the actual risks involved, consumers are likely less receptive to buy leafy greens irrigated with treated wastewater, also known as reclaimed water. In this study, we aimed to assess the microbiological risks of leafy green vegetables irrigated with treated wastewater in Spain using Norovirus as a model organism to facilitate the development of risk management strategies. A conceptual exposure model was designed to describe the virus fate and transport from the Wastewater treatment plant (WWTP) secondary effluent to the consumers' fork. This study is an example of the use of reclaimed water for irrigation of commercial fields producing leafy greens in the south‐east of Spain and tries to assess potential microbiological risks to the consumers by establishing their safety.

Urban water as an alternative freshwater resource for matching irrigation demand in the Bengal delta

Rapid changes in climate patterns, population growth, urbanization, and rising economic activities have increased the pressure on the delta's freshwater availability. Bangladesh's coastal planes suffer from a shortage of good quality irrigation water, which is crucial for peri-urban agriculture and at the same time, a high volume of untreated wastewater is discharged into the surface water. This calls for a transition towards efficiently managing and (re)using available urban water resources for irrigation, which is addressed in this paper. A quantitative match between the irrigation demand and potential freshwater supply has been assessed considering different urban water generation scenarios. The FAO AquaCrop model has been used to calculate the irrigation water demand for Boro rice during the dry period. Results indicate that 7.4 million m3 of irrigation water is needed, whereas over 8.2 million m3 of urban water is being generated during the dry season. Simultaneously, mismatches between irrigation demand and alternative water supply mainly occurred in February and March, which could be resolved with water storage capacities. However, to make urban water reuse a reality, the water management policy needs to change to facilitate the construction of required infrastructures for collection, treatment, and storage. The proposed method helps realize the urban water's hidden potential to sustain agricultural activities in the delta areas.

Impact of Rainfall Trend on Irrigated Agriculture of Narayanapura Command in a Semi-Arid Region of South India

Water demands have been exacerbated by the uncertainty in rainfall occurrences and distribution due to various factors in a changing climate and growing population. The irrigation sector has the highest water demand, accounting for 85 percent of total water use in Karnataka. Rainfall plays a critical part in meeting irrigation needs. To effectively allocate and manage water resources for command area management, examining rainfall patterns, distribution of rainfall trends, both regional and temporal variations is necessary. Hence, the primary focus of this research is to investigate the impact of rainfall trends on agricultural water requirements for a typical study area in semi-arid region.
 To assess the rainfall trend, time-series statistical trend tests called Mann–Kendall (MK) test and the Innovative Trend Analysis (ITA) approach are used to examine the spatio-temporal distributions of long-term rainfall patterns for the Narayanapura command region. The results are then geo-processed to examine the spatial distribution of trends using the isohyetal concept. The findings illustrate the spatial distribution of rainfall trend for the command in a semi-arid region on a monthly, monsoon, and annual basis.
 Spatio-temporal analyses from both methodologies indicates the trend in rainfall pattern is decreasing annually and in monsoon months, with a rising trend for pre-monsoon showers. The trend variation pattern also reveals periodic oscillation alignment in the direction of south-west monsoon movement. According to MK test results, monsoon rainfall is anticipated to decrease by 12 percent by 2047, and by 21 percent from ITA results. Further, impact analysis indicates that, for every unit millimeter of rainfall deficit, there would be a 62 Ha-m increase in irrigation water demand.

GENERATING RATING CURVE AND RATING TABLE OF GOLARCHI MINOR

Hydrologists must have huge theoretical and practical knowledge of irrigation networks such as rivers, canals, streams, channels, and minors. Because whole irrigation system relies on a gauge and discharges relationship which is essential for controlling floods, water resource management, and hydrologic modeling. The true and consistent figures of flow rate in the irrigation system are important for irrigation water efficiency. Mostly, Hydrologic modeling activities like hydraulic structures, designs, and management of surplus water in canals are subjected to the flow of irrigation water which is derived from the rating curve (RC). The managing of irrigation water in the system must be essential for crop water requirements and estimation of seepage losses. Thus, to fulfill the objectives, field activities (discharge measurement) were conducted in Golarchi minor of the Left-bank area water board. The main target was to calculate real discharge at different gauge levels and to develop a rating curve and rating table for the accurate distribution of irrigation water in the command area. Hence, the discharge was measured with a current meter and the area velocity method was employed for flowing water. The discharge was taken at three different gauges i.e., 1.2ft, 1.34ft, and 1.55ft with the discharge of 51.921cusecs, 55.021cusecs, and 58.197cusecs. Then collected data was exported to MS Excel for manipulation and for developing rating curves. The power equation was developed for Golarchi minor for confirming the different discharges on different gauge heights. The results of the study calculated as 1.1ft gauge to 1.7ft gave discharge 50.383cusecs to 61.009cusecs. It is concluded that the present study suggested that there should have an automatic gauging station to know the real demand for irrigation water in the command area and di-siltation should be done.