Irrigation Wells Research Articles

Role of Multiple High-Capacity Irrigation Wells on a Surficial Sand and Gravel Aquifer

Within McHenry County, IL, the fastest growing county in Illinois, groundwater is used for 100% of the water needs. Concerns over water resources have prompted the investigation of the surficial sand and gravel aquifers of the county. While the eastern portion of the county is urbanizing, the western portion remains devoted to agriculture. High-capacity irrigation wells screened within the surficial sand and gravel aquifer are used for crop production. To assess the impacts of the irrigation wells on the aquifer, a groundwater flow model was developed to examine five different scenarios reflecting drought conditions and increased pumping. Results show that the surficial sand and gravel aquifer is capable of meeting current water demands even if recharge is decreased 20% and pumping is increased 20%. The additional loss of discharge and increases in pumping result in head differences throughout the aquifer.

Analytical modeling of irrigation and land use effects on streamflow in semi-arid conditions

Summary Availability and uncertainty in input data are the primary constraints of groundwater modeling. Analytical models assimilate the key and important data, but capture the major traits of the watershed. We study a baseflow-dominated stream, Frenchman Creek in southwestern Nebraska, USA, which has experienced large streamflow reductions since the 1960s and is a subject of various actions on water rights appropriation. The new element of the model is simultaneous analytical consideration of groundwater pumping and land use change effects. Analytical stream depletion rate calculations by various methods show that pumping from the 462 irrigation wells in the basin consumed a large amount of baseflow. The simulated streamflow at the outlet of Frenchman Creek with minimal calibration compares favorably with observed streamflow and indicates the viability of an analytical approach to watersheds with limited hydrogeologic data.

An integrated hydrogeological study to support sustainable development and management of groundwater resources: a case study from the Precambrian Crystalline Province, India

The rapid expansion of agriculture, industries and urbanization has triggered unplanned groundwater development leading to severe stress on groundwater resources in crystalline rocks of India. With depleting resources from shallow aquifers, end users have developed resources from deeper aquifers, which have proved to be counterproductive economically and ecologically. An integrated hydrogeological study has been undertaken in the semi-arid Madharam watershed (95 km2) in Telangana State, which is underlain by granites. The results reveal two aquifer systems: a weathered zone (maximum 30 m depth) and a fractured zone (30–85 m depth). The weathered zone is unsaturated to its maximum extent, forcing users to tap groundwater from deeper aquifers. Higher orders of transmissivity, specific yield and infiltration rates are observed in the recharge zone, while moderate orders are observed in an intermediate zone, and lower orders in the discharge zone. This is due to the large weathering-zone thickness and a higher sand content in the recharge zone than in the discharge zone, where the weathered residuum contains more clay. The NO3− concentration is high in shallow irrigation wells, and F− is high in deeper wells. Positive correlation is observed between F− and depth in the recharge zone and its proximity. Nearly 50 % of groundwater samples are unfit for human consumption and the majority of irrigation-well samples are classed as medium to high risk for plant growth. Both supply-side and demand-side measures are recommended for sustainable development and management of this groundwater resource. The findings can be up-scaled to other similar environments.

Radiological Quality of Water in Areas with Old Uranium Mines in the District of Viseu, Portugal

Radionuclides were determined in streams and rivers receiving mine drainage in areas of old uranium mines at the centre of Portugal. Results showed enhanced radioactivity levels in some areas impacted by uranium mining and milling wastes, but lower than several years ago. Current treatment of mine drainage contributed to decrease radioactivity levels in streams. In some horticulture areas, such as at Cunha Baixa, water from irrigation wells was contaminated by acid mine drainage and is not suitable for human consumption and for irrigation. Villages and towns near those old uranium mines currently have tap water from public networks supplied from artificial lakes in major rivers of the region. This tap water showed compliance with the recommended limits of total alpha and total beta radioactivity and is suitable for human consumption.

Environmental Radioactivity in the Sabugal Region and Impact of Past Uranium Mining

An environmental radioactivity survey carried out in the Sabugal region, Portugal, showed enhanced radioactivity levels in surface water streams related to water discharges from old uranium mines. Water from irrigation wells in this region displayed variable radionuclide levels due to natural occurrence of radionuclides and also to contamination by mine water drainage. Horticulture products grown near the uranium mine sites contained elevated radium (226Ra) concentrations but lower concentrations of uranium and other radionuclides. Despite relatively elevated radioactivity in irrigation water, the absorption and accumulation of radionuclides in plants was limited. Taking into consideration the volume of uranium waste piles, the improved management of mine waste and mine drainage is needed in order to prevent the increase of environmental radioactivity in the area.

Evaluating Groundwater Pollution Using Hydrochemical Data: Case Study (Al Wahat Area East of Libya)

Water is one of the most challenging current and future natural resources, which will directly affect the environment and development by the changes in its quantity, quality and regional distribution. However, Water quality is the critical factor that influences human health and irrigation proposer. This work aims to investigate hydrochemical analysis and geochemical processes influencing the groundwater of Al Wahat area (Jalou, Awjla and Jukherra), which is located in central east Libya. Thirty four water samples collected from domestic and agricultural water wells were analyzed and used for conventional classification techniques which were Piper, Durov and Stiff diagrams to evaluate geochemical processes. Cluster analysis was used to identify the water type and ions concentration and distribution. Results show significant increase of dissolved salts, especially Nitrates. Elevated nitrates concentration can be attributed to either the disposal of untreated sewage water from disposal ponds and septic tanks or the infiltration of irrigation water saturated with fertilizing chemicals. Therefore, irrigation wells revealed that suffering from nitrate contamination caused an increase of the chance of nitrate pollution. In addition, contour maps present a sudden increase in the total dissolved salts (TDS) in the northeastern part coincident with the highest of secondary ions of NO3 content, indicating the infiltration of irrigation water which is responsible partially for the groundwater degradation. Hydrogeochemical facie is NaCl type and enrichment of Na+ and Cl- can be attributed to urban untreated wastewaters and high rate of evapotranspiration. The concentrations of heavy elements such as Zn, Pb, Cu, Cd, Ni and Cr were low and within the WHO ranges.

Microextraction by packed sorbent coupled with gas chromatography–mass spectrometry: A comparison between “draw-eject” and “extract-discard” methods under equilibrium conditions for the determination of polycyclic aromatic hydrocarbons in water

In this work, two different extraction procedures for the analysis of different polycyclic aromatic hydrocarbons (PAHs) in water by microextraction by packed sorbent (MEPS) have been compared in terms of sensitivity, reliability and time of analysis. The first method, called “draw-eject”, consists of a sequence of cycles of aspirations and injections in the same vial; the second one, called “extract-discard”, consists of a similar cycle sequence, but the aspired sample in this case is discarded into waste. The relevant partition equilibriums and extraction rates have been calculated by multivariate regression from the data obtained after MEPS gas chromatography–mass spectrometry (MEPS-GC–MS) analysis of 16 PAHs from water samples. Partitioning parameters for a priori prediction of solute sorption equilibrium, recoveries and preconcentration effects in aqueous and solvent systems have been calculated and compared for the two extraction procedures. Finally, real samples from sea, agricultural irrigation wells, streams and tap water were analyzed. Detection (S/N≥3) and quantification (S/N≥10) limits were calculated for the extraction processes. Under the experimental conditions used for the “draw-eject” procedure, these values were in the range 0.5–2ngL−1 and 1.6–6.2ngL−1, while for the “extract-discard” procedure they ranged from 0.2 to 0.8ngL−1 and from 0.8 to 2.0ngL−1, respectively.

Stochastic Simulation and Management of an Over-Exploited Aquifer Using an Integrated Modeling System

A modeling system for the stochastic simulation and management of the overexploited groundwater resources of Lake Karla Basin in Central Greece is presented. The uncertainty of the hydrogeological environment which arises from the lack of the hydraulic conductivity data and aquifer’s heterogeneity necessitates the stochastic simulation of the underlying aquifer. For the conditional stochastic simulation of hydraulic conductivity, the geostatistical approach was used generating Monte-Carlo realizations. The impact of Lake Karla (or reservoir) restoration and the accompanying projects on the aquifer, is examined through various management scenarios taking into consideration this parameter uncertainty. The target of the restoration plan is to rehabilitate aquifer’s water table. This will be achieved through shutting down a great number of irrigation wells, as the irrigation needs of cultivations will be covered by the reservoir. The project with the highest environmental impact on the aquifer is the construction of 50 water supply wells at the lakeside zone of Lake Karla. Nowadays, due to the intense agricultural cultivation, the study area faces a serious water deficit problem, which has led to the over-exploitation of non-renewable groundwater and to a dramatic drawdown of aquifer’s water table. The results of the stochastic simulation and management indicates that the operation of the new water supply wells will lead, despite the operation of the new reservoir, to a further drawdown of aquifer’s water table, and will increase the effect of parameter uncertainty on hydraulic heads estimation by groundwater model.

Hydrogeological investigation for assessment of the sustainability of low-arsenic aquifers as a safe drinking water source in regions with high-arsenic groundwater in Matlab, southeastern Bangladesh

• The risk of cross-contamination of deep aquifers by As in Bangladesh was assessed. • Groundwater flow simulations identified regional and local flow-systems. • Cross-contamination is likely to be limited to areas with many irrigation wells. • When groundwater at depth has low As, it can be used for drinking water purposes. • However, installation of deep irrigation wells is strongly discouraged. Exploitation of groundwater from shallow, high prolific Holocene sedimentary aquifers has been a main element for achieving safe drinking water and food security in Bangladesh. However, the presence of elevated levels of geogenic arsenic (As) in these aquifers has undermined this success. Except for targeting safe aquifers through installations of tubewells to greater depth, no mitigation option has been successfully implemented on a larger scale. The objective of this study has been to characterise the hydrostratigraphy, groundwater flow patterns, the hydraulic properties to assess the vulnerability of low-arsenic aquifers at Matlab, in south-eastern Bangladesh, one of the worst arsenic-affected areas of the country. Groundwater modelling, conventional pumping test using multilevel piezometers, hydraulic head monitoring in piezometer nests, 14 C dating of groundwater and assessment of groundwater abstraction were used. A model comprising of three aquifers covering the top 250 m of the model domain showed the best fit for the calibration evaluation criteria. Irrigation wells in the Matlab area are mostly installed in clusters and account for most of the groundwater abstraction. Even though the hydraulic heads are affected locally by seasonal pumping, the aquifer system is fully recharged from the monsoonal replenishment. Groundwater simulations demonstrated the presence of deep regional flow systems with recharge areas in the eastern, hilly part of Bangladesh and shallow small local flow systems driven by local topography. Based on modelling results and 14 C groundwater data, it can be concluded that the natural local flow systems reach a depth of 30 m b.g.l. in the study area. A downward vertical gradient of roughly 0.01 down to 200 m b.g.l. was observed and reproduced by calibrated models. The vertical gradient is mainly the result of the aquifer system and properties rather than abstraction rate, which is too limited at depth to make an imprint. Although irrigation wells substantially change local flow pattern, targeting low-As aquifers seems to be a suitable mitigation option for providing people with safe drinking water. However, installing additional irrigation- or high capacity production wells at the same depth is strongly discouraged as these could substantially change the groundwater flow pattern. The results from the present study and other similar studies can further contribute to develop a rational management and mitigation policy for the future use of the groundwater resources for drinking water supplies.

Environmental fate of soil applied neonicotinoid insecticides in an irrigated potato agroecosystem.

Since 1995, neonicotinoid insecticides have been a critical component of arthropod management in potato, Solanum tuberosum L. Recent detections of neonicotinoids in groundwater have generated questions about the sources of these contaminants and the relative contribution from commodities in U.S. agriculture. Delivery of neonicotinoids to crops typically occurs as a seed or in-furrow treatment to manage early season insect herbivores. Applied in this way, these insecticides become systemically mobile in the plant and provide control of key pest species. An outcome of this project links these soil insecticide application strategies in crop plants with neonicotinoid contamination of water leaching from the application zone. In 2011 and 2012, our objectives were to document the temporal patterns of neonicotinoid leachate below the planting furrow following common insecticide delivery methods in potato. Leaching loss of thiamethoxam from potato was measured using pan lysimeters from three at-plant treatments and one foliar application treatment. Insecticide concentration in leachate was assessed for six consecutive months using liquid chromatography-tandem mass spectrometry. Findings from this study suggest leaching of neonicotinoids from potato may be greater following crop harvest in comparison to other times during the growing season. Furthermore, this study documented recycling of neonicotinoid insecticides from contaminated groundwater back onto the crop via high capacity irrigation wells. These results document interactions between cultivated potato, different neonicotinoid delivery methods, and the potential for subsurface water contamination via leaching.

Nebraska's groundwater legacy: Nitrate contamination beneath irrigated cropland.

A 31 year record of ∼44,000 nitrate analyses in ∼11,500 irrigation wells was utilized to depict the decadal expansion of groundwater nitrate contamination (N ≥ 10 mg/L) in the irrigated corn-growing areas of eastern and central Nebraska and analyze long-term nitrate concentration trends in 17 management areas (MAs) subject to N fertilizer and budgeting requirements. The 1.3 M contaminated hectares were characterized by irrigation method, soil drainage, and vadose zone thickness and lithology. The areal extent and growth of contaminated groundwater in two predominately sprinkler-irrigated areas was only ∼20% smaller beneath well-drained silt loams with thick clayey-silt unsaturated layers and unsaturated thicknesses >15 m (400,000 ha and 15,000 ha/yr) than beneath well and excessively well-drained soils with very sandy vadose zones (511,000 ha and 18,600 ha/yr). Much slower expansion (3700 ha/yr) occurred in the 220,000 contaminated hectares in the central Platte valley characterized by predominately gravity irrigation on thick, well-drained silt loams above a thin (∼5.3 m), sandy unsaturated zone. The only reversals in long-term concentration trends occurred in two MAs (120,500 ha) within this contaminated area. Concentrations declined 0.14 and 0.20 mg N/L/yr (p < 0.02) to ∼18.3 and 18.8 mg N/L, respectively, during >20 years of management. Average annual concentrations in 10 MAs are increasing (p < 0.05) and indicate that average nitrate concentrations in leachates below the root zone and groundwater concentrations have not yet reached steady state. While management practices likely have slowed increases in groundwater nitrate concentrations, irrigation and nutrient applications must be more effectively controlled to retain nitrate in the root zone.

The role of groundwater trading in spatial water management

Agricultural groundwater use is increasingly being restricted to address the negative impacts of pumping on instream flows for downstream users, endangered species habitat, and recreation. Understanding the spatial heterogeneity of the costs of water use restrictions to farmers is critical to evaluating the effectiveness of current and alternative water management policies. We use a geospatial population dataset of irrigation wells in the Republican River Basin of Nebraska and model the simultaneous crop choice, land and water use decisions at a well level. We estimate the magnitude and distribution of costs of current groundwater restrictions as well as cost savings from alternative market-based policies that allow trading of permits between farmers. Our analysis highlights the importance of the initial distribution of permits and the institutional context in which trading occurs. Both allocated but unused permits and land estimated to move from irrigated to dryland crops provide important trading volume into the water rights market. The results show that the cost savings from allowing trading of groundwater pumping rights are distributed unevenly between wells, counties, and groundwater management institutions.

Optimal management of groundwater pumping of the cache critical groundwater area, Arkansas

A simulation model for part of the Mississippi River Valley alluvial aquifer in the Cache area, Arkansas, was coupled with an optimization model to determine maximum optimal pumping from irrigation wells in the areas where cones of depression exist. Groundwater Vistas and Groundwater Management software were used for simulation and optimization model, respectively. The Cache area was designated as a critical groundwater area in 2009 due to the decline in its water level to below 50 % of the saturated thickness of the aquifer. The optimization model was formulated with the objective of maximizing water production from wells subjected to minimum head constraints and drawdown constraints, while limiting groundwater withdrawals to a maximum of 100 and 200 % of the rate pumped in 2010. Four different sets of managed wells were tested in Scenarios 1, 3 (938 wells) and Scenarios 2, 4 (3870 wells). The optimal pumping rates from groundwater in the case of minimum head constraints were 0.59 and 2.43 Mm3/d for Scenarios 1 and 2, respectively. In the case of maximum pumping constraints of the managed wells specified as 200 % of the pumping rate of 2010, the optimal pumping rates from groundwater in the case of minimum head constraints were 0.88 and 3.28 Mm3/d for Scenarios 3 and 4, respectively. The average optimal pumping increased by 6–49 % in the case of the maximum pumping constraint specified as 200 % of the pumping rate of the year 2010.

Variables that Affect Agricultural Chemicals in Groundwater in Nebraska

Agricultural chemicals from nonpoint sources in groundwater are present in the major provinces of the High Plains aquifer in Nebraska. Nitrate and triazine-herbicide concentrations in groundwater were assessed to establish preliminary relations between these constituents and selected hydrogeologic, climatic, and land-use variables. Also, macropore flow paths were measured in an attempt to delineate their contribution to non-point source pollution from the study areas. Water from 82 wells in six study areas was analyzed for nitrate; water from 57 of the 82 wells was analyzed for triazine herbicides. Twenty-one independent variables were identified that could potentially affect chemical concentrations in groundwater. Data for 9 of 21 independent variables suspected of affecting concentrations of nitrate and triazine herbicides in groundwater were collected from the well sites. The nine variables and their measured ranges were hydraulic gradient, 0.0006–0.0053; hydraulic conductivity, 1.5–45.4 m (5–149 ft) per day; specific discharge, 0.004–0.091 m (0.0128–0.2998 ft) per day; depth to water, 0.91–76 m (3–250 ft); well depth, 12–168 m (40–550 ft); annual precipitation, 30–100 cm (12.0–39.3 in.); soil permeability, 1.9–23 cm (0.76–9.0 in.); irrigation-well density, 0–8 irrigation wells per 2.59 km2 (1 square mile); and annual nitrogen fertilizer use, 0–118 kg (0–260 lb) of nitrogen per acre. Macropore flow is listed in percent, average per study area based on determinations from dye studies. In this instance, macropore flow is used to also entail preferential flow paths. Nitrate concentrations ranged from 0.1 to 45 mgL−1. Triazine-herbicide concentrations were detected in samples from five of the six study areas in concentrations ranging from 0.1 to 2.3 μL−1. Analysis indicated that there were significant differences in nitrate concentrations (averages—at 95 % confidence level using Kendall Test) among the six study areas; no significant differences in triazine-herbicide concentrations were found. Concentrations of nitrate and triazine herbicide were determined (using contingency-table analysis), to be significantly larger in more intensively irrigated areas compared to less intensively irrigated areas. Preliminary correlations with the independent variables and nitrate concentrations indicated significant relations at the 95 % confidence level with variables hydraulic conductivity, well depth, and irrigation well density. Correlations with triazine-herbicide concentrations indicated significant relations with hydraulic conductivity, specific discharge, well depth, annual precipitation, and irrigation well density, as well as nitrate concentrations. Simple multiple-regression technique indicated that well depth and density and fertilizer use explained about 51 % of the variation in nitrate concentrations. Specific discharge and well depth explained about 60 % of the variation in triazine-herbicide concentrations. Macropore flow paths and specific discharge explained 84 % of the total variation in triazine-herbicide concentrations. The use of trade names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey.

Radioactivity in Soils and Vegetables from Uranium Mining Regions

Samples of soils, irrigation water, and vegetable products from three areas were analyzed for radionuclides. These areas are located in the basins of Ribeira da Pantanha, Ribeira do Castelo and streams tributaries to Ribeira de Inguias, all receiving drainage from old uranium mines. Results showed enhancement of radionuclide concentrations, especially 226Ra, in vegetables from kitchen gardensin these areas when compared with reference areas upstream the mine‘s discharge points.The main source and transfer pathway of radionuclides to plants was the irrigation water used, rather than the soil. Non-contaminated products were obtained in these areas when irrigation was made with non-contaminated water from deep wells, instead of water from surface streams and irrigation wells contaminated with mine drainage. Guidelines for radionuclide concentrations in irrigation water and soil are needed.

Wireless Group Control System Applied in Plantation Irrigation System

This paper have a study of the wireless group control system applied in plantation irrigation system. China is a fresh water resources scarce country, agricultural irrigation occupies a large part of the water resources. Because long-term use of traditional farming patterns, low utilization rate of irrigation water, irrigation water wasted is a very serious problem. In order to improve the irrigation efficiency and spare the water resource, based on an example of a large plantation in Shandong Province, this study designs a wireless group control system according to the specific situation of the irrigation wells dispersed. It realizes the communication between the main control room and 13 dispersed wells through wireless network. In the distributed sub-stations, we use the Frequency Converter to drive the lift pump to achieve the precise allocation of irrigation water, the saving effect is significant. Besides, the paper especially introduces the software realization of the wireless communication.

An Estimation of the Private Value of Aquifer Recharge from Ephemeral Wetlands on the Texas High Plains

Ecosystem services are benefits people derive from resources in ecosystems. Playa lakes in the Southern High Plains region of North America provide several ecosystem services for humans, including recharge to the Ogallala aquifer. The Ogallala aquifer occupies 450,000 km2, it is part of eight states, and provides irrigation water to over 25% of the irrigated land in the United States. The recharge provided by playas potentially makes them important and valuable in this region. We develop an econometric model (with spatial aspects) to determine how playas affect the water level of irrigation wells and estimate the economic value to farmers of playa ecosystem services in recharging the water in those wells. We find that, in some instances, additional playa surface area may have a small but statistically significant effect on well drawdown (and, we infer, on recharge) on nearby wells, but that the value of the additional water is likely too small to significantly affect private management decisions. Because of lack of appropriate data, these results are of only limited applicability. We therefore identify a need for more research on the effects of management of sedimentation of playa wetlands as a key component that may improve the findings reported here.

The regulation of a spatially heterogeneous externality: Tradable groundwater permits to protect streams

Groundwater pumping can reduce the flow of surface water in nearby streams. In the United States, recent awareness of this externality has led to intra- and inter-state conflict and rapidly-changing water management policies and institutions. Although the marginal damage of groundwater use on stream flows depends crucially on the location of pumping relative to streams, current regulations are generally uniform over space. We use a population data set of irrigation wells in the Nebraska portion of the Republican River Basin to analyze whether adopting spatially differentiated groundwater pumping regulations leads to significant reductions in farmer abatement costs and costs from damage to streams. We find that regulators can generate most of the potential savings in total social costs without accounting for spatial heterogeneity. However, if regulators need to increase the protection of streams significantly from current levels, spatially differentiated policies will yield sizable cost savings.

Geophysical characterization of the complex dynamics of groundwater and seawater exchange in a highly stressed aquifer system linked to a coastal lagoon (SE Spain)

Anthropogenic pressure influences the two-way interactions between shallow aquifers and coastal lagoons. Aquifer overexploitation may lead to seawater intrusion, and aquifer recharge from rainfall plus irrigation may, in turn, increase the groundwater discharge into the lagoon. We analyse the evolution, since the 1950s up to the present, of the interactions between the Campo de Cartagena Quaternary aquifer and the Mar Menor coastal lagoon (SE Spain). This is a very heterogeneous and anisotropic detrital aquifer, where aquifer–lagoon interface has a very irregular geometry. Using electrical resistivity tomography, we clearly identified the freshwater–saltwater transition zone and detected areas affected by seawater intrusion. Severity of the intrusion was spatially variable and significantly related to the density of irrigation wells in 1950s–1960s, suggesting the role of groundwater overexploitation. We distinguish two different mechanisms by which water from the sea invades the land: (a) horizontal advance of the interface due to a wide exploitation area and (b) vertical rise (upconing) caused by local intensive pumping. In general, shallow parts of the geophysical profiles show higher electrical resistivity associated with freshwater mainly coming from irrigation return flows, with water resources mostly from deep confined aquifers and imported from Tagus river, 400 km north. This indicates a likely reversal of the former seawater intrusion process.

Maize Evapotranspiration, Yield Production Functions, Biomass, Grain Yield, Harvest Index, and Yield Response Factors under Full and Limited Irrigation

<abstract><title><italic>Abstract.</italic></title> South-central Nebraska is one of the most extensively irrigated areas in the U.S., with over 65,000 active irrigation wells, and maize is the major agronomical crop produced. Maize production in this region requires supplementary irrigation for maximum productivity. Effective on-farm implementation of full and limited irrigation practices for potential improvements of crop productivity requires knowledge of locally developed crop yield response to water functions. In this study, the effects of full and limited irrigation practices on maize (Zea mays L.) plant height, leaf area index (LAI), grain yield and biomass production, actual crop evapotranspiration (ET_a), yield production functions, yield response factors (K_y), and harvest index (HI) were investigated. Field experiments were conducted in 2009 and 2010 under center-pivot irrigation at the University of Nebraska-Lincoln, South Central Agricultural Laboratory near Clay Center, Nebraska. Four irrigation regimes [fully irrigated treatment (FIT), 75% FIT, 60% FIT, and 50% FIT] and a rainfed treatment were evaluated each year. Maize ET_a, LAI, biomass production, grain yield, and HI were significantly affected by the irrigation regimes. Maize yields varied from 9.05 Mg ha^-1 for the rainfed treatment to 15.5 Mg ha^-1 for FIT in 2009 and from 11.7 to 15.5 Mg ha^-1 for the respective treatments in 2010. HI ranged between 0.49 for rainfed and 0.57 for FIT with an all-treatment average of 0.54. ET_a ranged from 481 mm for rainfed treatment to 620 mm for FIT in 2009 and from 579 to 634 mm for the same treatments in 2010. Strong yield vs. irrigation relationships (R² ≥ 0.98 in both years) and yield vs. ET_a relationships (R² = 0.94 in 2009 and R² = 0.97 in 2010) were measured. There was a strong linear increase in ET_a with increasing irrigation amounts (R² ≥ 0.97). The yield-irrigation and yield-ET_a relationships showed variation between the two years due to the impact of weather variability on these relationships, indicating the importance of accounting for weather variability impact on the slopes of crop yield production functions. Based on the slopes of the ET_a vs. grain yield relationships, 1.2 Mg ha^-1 (in 2009) and 1.7 Mg ha^-1 (in 2010) of grain yield was produced per 25.4 mm of ET_a beyond 280 mm (in 2009) and 403 mm (in 2010) of ET_a that was used by maize to start producing grain yield, which is also called the amount of ET_a required for establishing grain yield. Yield response factors varied between treatments and with year for the same treatment and averaged 1.65 in 2009 and 2.85 in 2010, with a two-year average of 1.82. No statistically significant difference (p > 0.05) in grain yield was found between 75% FIT and 100% FIT. In terms of crop response to water performance, the 75% FIT and 60% FIT treatments were very comparable to the fully irrigated treatment and are viable practices in increasing crop water productivity of maize with supplementary irrigation under these experimental, soil and crop management, and climatic conditions.