Research articleLandscape irrigation management for maintaining an aquifer and economic returns
Introduction
Groundwater is a vital component of the earth's water resources. Nearly all community water systems in rural America rely on groundwater, and in times of drought groundwater feeds streams and rivers to provide environmental benefits. Roughly 42 percent of agricultural irrigation water in the United States is obtained from groundwater (National Groundwater Association, 2010). Due to the reliance of irrigated crops on groundwater, many shallow aquifers have declined over the past century by several hundred feet. This raises the cost of pumping groundwater and puts at risk the economic returns of agriculture. However, the tradeoff between the aquifer volume and economic returns for a spatially explicit landscape has not been explored for a model using a large selection of crop types and irrigation practices. We believe by quantifying this tradeoff that this will aid the conversation between agricultural producers and groundwater regulators about the balance of the aquifer conservation and economic returns.
Successful conservation requires taking aquifer depletion into account across the entire agricultural landscape where the spatial mix of crops grown that affect groundwater cones of depression matter as much as the total amount groundwater pumped. There are some crops that generate valuable economic returns that are also consistent with at least some groundwater conservation. Natural recharge can sustain an aquifer while some level of irrigated agriculture remains on the land above. The broader environmental management question, beyond where are the best places to adopt water-saving irrigation technologies, is whether aquifer conservation is possible on a landscape with both irrigated and dryland agriculture. While farm production decisions based solely on economic returns can be detrimental to the aquifer, securing some economic return from farm land need not be mutually exclusive with a sustainable aquifer. Careful consideration of the pattern, extent, and intensity of crop production across the landscape can achieve a desired aquifer level while also generating reasonable economic returns. By encouraging multiple irrigation practices, this can enhance economic returns and affect the tradeoff between conservation and economic returns.
Spatially explicit aquifer and economic models are integrated to analyze the consequences of alternative crop type and irrigation decisions for aquifer and economic objectives. The aquifer model evaluates how well groundwater can be sustained on a large landscape given a spatially explicit pattern of crop types and irrigation practices. The aquifer's thickness, hydro-conductivity, and distance to surrounding grid cells affect the underground flow of the aquifer due to pumping on each grid cell. Based on the irrigation demand of the crop types and underground aquifer flow, we estimate the depletion of the aquifer under each grid cell. By summing the aquifer depletion over all cells, we track the total volume of the aquifer. The economic model predicts the economic returns for each grid cell under different crop types, including irrigated rice, soybeans, corn, and cotton, as well as non-irrigated soybeans, sorghum, and wheat. Location specific soil characteristics and initial depth to the aquifer affects the yield of the crops and groundwater pumping cost. The pumping cost of groundwater increases as the aquifer is depleted. Irrigation practices influence the yield, demand for irrigation water, and production cost of the crops. We combine commodity prices data with yields and production costs to generate economic returns for these crop types. The total economic return is the sum of the present value of crop returns of all grid cells.
We combine results from the aquifer and economic models to search for optimal crop and irrigation practice patterns. An efficient pattern generates the maximum economic return for a given volume of the aquifer sustained. By maximizing the economic returns over the entire range of possible aquifer volumes, an efficiency frontier is created for the landscape. The frontier illustrates what can be achieved in terms of aquifer and economic objective by careful spatial arrangement of crop types and irrigation practices. The efficiency frontier also demonstrates the degree of inefficiency of arrangements not on the frontier.
The application of the model is to the Mississippi River Valley Alluvial Aquifer (MRVA), the third most used aquifer in the United States. The sustainability of the MRVA is vital to maintaining long-term agricultural profitability in the Lower Mississippi River Basin (LMRB), one of the most productive agricultural regions in the United States (Maupin and Barber, 2005, Konikow, 2013). Arkansas is the largest consumer of water from the aquifer (Maupin and Barber, 2005), and the current rate of withdrawals from the aquifer is not sustainable although irrigated acres continues to increase each year (Barlow and Clark, 2011, ANRC, 2012). The LMRB has average annual precipitation ranging from 50 to 57 inches per year and is thus often considered an area rich in water resources (NOAA, 2014). However, the lack of timely rainfall and the use of irrigation to increase yields have meant the increasing installation of irrigation wells. A number of counties in east Arkansas have been designated as critical groundwater areas due to the continued decline in groundwater levels (ANRC, 2012). Studies predict that some parts of the alluvial aquifer will become commercially useless as early as 2015 if current pumping levels continue uncurbed (Sullivan and Delp, 2012). Federal programs have contributed to the voluntary implementation of alternative irrigation practices such as on-farm storage reservoirs, tail-water recovery ditches, and sensor technologies, among others.
While there is a large literature on multi-objective analysis in water resource planning (see Hajkowicz and Collons, 2007; for a recent review), much of this literature focuses on efficient water policy and supply planning. This literature typically does not incorporate analysis of working agricultural lands, either in terms of the landscape's ability to sustain an aquifer or in terms of economic returns. Water supply planning (Joubert et al., 2003) and infrastructure selection (Eder et al., 1997) have impacts on numerous stakeholders and must handle multiple objectives for which multi-criteria analysis is well-suited. Several papers have used multi-criteria analysis to incorporate infrastructure costs and economic returns in water resource planning (e.g. Mimi and Sawalhi, 2003, Karnib, 2004, Raju and Nagesh Kumar, 1999, Cai et al., 2004). Almost all prior work that combines water models of aquifer depletion and economic models to evaluate conservation and economics returns focus on a single irrigation technology or a single crop such as cotton or corn (e.g. Darouich et al., 2012, Gillig et al., 2004, Rodrigues et al., 2013).
The papers closest to our paper in terms of analyzing multiple irrigation technologies and multiple crops while comparing objectives such as aquifer conservation and economic returns are those by McPhee and Yeh (2004) and Xevi and Khan (2005). McPhee and Yeh (2004) derive the tradeoffs among three competing objectives by minimizing the magnitude and extent of drawdown of an aquifer. Xevi and Khan (2005) analyze the conflicts that arise between profitability, variable costs of production, and pumping of groundwater for multiple crops within a network of reservoirs, canals, and irrigation districts. Neither of these papers though considers the optimized configuration of the landscape in their study of sustained aquifer and economic return tradeoffs.
In the next section we describe the land, water, and economic models as well as the optimization algorithm used to find efficient land and water patterns. The section that follows describes the data for the application of the approach to the Arkansas side of the Mississippi Delta. The last two sections include the results and a conclusion with a discussion of the methods and results.
Section snippets
Methods
The crops grown in the farm production region of the Arkansas Delta depend on the land suitability and on the supply of water in the underlying aquifer. A grid of m cells (sites) represents spatially specific crop yields associated with soil quality and spatially symmetric cones of depression from groundwater pumping with the available groundwater based on the pumping decisions of farms in and around the site weighted by distance. The time frame is the 30 year period from 2013 to 2043.
Data
The study area is comprised of three eight-digit hydrodologic unit code (HUC) watersheds1 where unsustainable groundwater use is occurring in the Arkansas Delta (Fig. 1). The watersheds overlap eleven Arkansas counties, and the study area is divided into 2724 sites to evaluate how a spatially differentiated landscape affects farmer decisions about crop allocation and water use. The initial acreage of crops in
Results
We find efficiency frontiers for aquifer conservation and economic returns in the Arkansas Delta (shown in Fig. 2) where only conventional irrigation is possible, shown by points A through E, and where all irrigation technologies are available, shown by points F to J. The tradeoffs inherent in the efficiency frontier with only conventional irrigation are presented first, and then the results are compared to the efficiency frontier using all irrigation technologies.
Starting from the crop pattern
Discussion
Our landscape level models of agricultural production and aquifer depletion considers crop, water, and irrigation technology choices to understand the tradeoff necessary between aquifer and economic impacts. Using the Arkansas Delta application, we find the possibility to maintain a high level of the aquifer and generate large economic returns through careful spatial management of crops. Recognizing dry land crops can generate profit with no pressure on the aquifer and comparatively low
Conclusion
Since few prior studies of multi-objective analysis in water resource planning integrate a spatial groundwater model with the principles of economic theory (Hajkowicz and Collons, 2007), much of the complexity in our model comes from a relatively new attempt to incorporate spatial patterns of groundwater pumping with farm production decisions. Many prior studies addressing multiple objectives have avoided this by considering only a single crop grown or by assuming that aquifer depletion occurs
Acknowledgements
Drs. Eric Wailes and Qiuqiong Huang provided helpful suggestions. Kuatbay Bektemirov provided excellent research assistance. This project was supported by the Arkansas Soybean Promotion Board and the US Geologic Survey of the 104b research grant program, US Department of the Interior, Grant #: G11AP20066.
References (37)
- et al.
On the spatial nature of the groundwater pumping externality
Resour. Energy Econ.
(2010) - et al.
Water saving vs. farm economics in cotton surface irrigation: an application of multicriteria analysis
Agric. Water Manag.
(2012) - et al.
Groundwater pumping and spatial externalities in agriculture
J. Environ. Econ. Manag.
(2012) - et al.
Multicriterion decision making in irrigation planning
Agric. Syst.
(1999) - et al.
Comparing sprinkler and drip irrigation systems for full and deficit irrigated maize using multicriteria analysis and simulation modelling: Ranking for water saving vs. farm economic returns
Agric. Water Manag.
(2013) - et al.
A multi-objective optimisation approach to water management
J. Environ. Manag.
(2005) Arkansas Groundwater Protection and Management Report for 2011
(2012)- et al.
Simulation of Water-use Conservation Scenarios for the Mississippi Delta Using an Existing Regional Groundwater Flow Model
(2011) - et al.
Streamflow Depletion by Wells-Understanding and Managing the Effects of Groundwater Pumping on Streamflow
(2012) - et al.
Group decision making in water resources planning using multiple objective analysis
J. Water Resour. Plan. Manag.
(2004)
Enhancements to the Mississippi Embayment Regional Aquifer Study (MERAS) Groundwater-flow Model and Simulations of Sustainable Water-level Scenarios
University of Arkansas. “2012 Crop and Enterprise Budgets.” Little Rock, AR: AG-1272
Ranking water resource projects and evaluating criteria by multicriterion Q-analysis: an Austrian case study
J. Multi-Criteria Decis. Anal.
Gasoline and Diesel Fuel Update
Economic efficiency and cost implications of habitat conservation: an example in the context of the Edwards Aquifer region
Water Resour. Res.
Charts and Quotes
A review of multiple criteria analysis for water resource planning and management
Water Resour. Manag.
Estimating Irrigation Costs
Cited by (5)
Increasing shrinkage risk of endorheic lakes in the middle of farming-pastoral ecotone of Northern China
2022, Ecological IndicatorsCitation Excerpt :The water requirement increased by more than 40% owing to the planting of crops with high water consumption (Huang et al., 2020). Extensive expansion of center pivot irrigation systems and other irrigation systems led to rates of aquifer extraction that far exceeded recharge (Pfeiffer and Lin, 2014), resulting in a decline in the groundwater table and drying of surface water (Kovacs et al., 2015). We extracted the seasonal and interannual variations in the lake surface area by combining MODIS NDVI and NDWI datasets in this semi-arid area.
Impact of center pivot irrigation on vegetation dynamics in a farming-pastoral ecotone of Northern China: A case study in Ulanqab, Inner Mongolia
2019, Ecological IndicatorsCitation Excerpt :Hence, herein we call this process “pseudo-improvement.” Extensive expansion of CPI led to rates of aquifer extraction that far exceeded recharge (Pfeiffer and Lin, 2014, Maldonado et al., 2018), resulting in a decline in the groundwater table (Kovacs et al., 2015, Duncan et al., 2016, Al Naber and Molle, 2017). For example, the ground-water table in some places of the United States, which first popularized CPI, dropped more than 1.5 m per year.
Water allocation and integrative management of precision irrigation: A systematic review
2020, Water (Switzerland)Influence analysis of sprinkler irrigation effectiveness using ANFIS
2019, International Journal of Agricultural and Biological EngineeringConjunctive water management to sustain agricultural economic returns and a shallow aquifer at the landscape level
2017, Journal of Soil and Water Conservation