Impacts of Crop Management and Climate Change on Hydrology Across the Wisconsin Central Sands

2014 Annual Report for GNC13-178

Project Type: Graduate Student
Funds awarded in 2013: $9,999.00
Projected End Date: 12/31/2015
Grant Recipient: University of Wisconsin
Region: North Central
State: Wisconsin
Graduate Student:
Faculty Advisor:
Dr. George Kraft
University of Wisconsin-Stevens Point
Faculty Advisor:
Dr. Christopher Kucharik
University of Wisconsin-Madison

Impacts of Crop Management and Climate Change on Hydrology Across the Wisconsin Central Sands


Pumping for irrigation in regions with strong ground-surface water connectivity can impact aquatic resources, leading to groundwater governance dilemmas. Recent hydrologic stresses and the decimation of local trout populations have created a groundwater governance dilemma between agricultural and aquatic stakeholders in the Wisconsin Central Sands, an ecological region with strong ground-surface water connectivity that has experienced changes in regional climate over the past 60 years. Sustainable agroecosystems in the Wisconsin Central Sands will maximize potato and maize production, while providing farmers with feasible irrigation strategies to protect prized freshwater lakes, streams, and wetlands. To this end, agricultural and aquatic stakeholders have continually met with scientists from academic institutions and government agencies to test assumptions, gather information, and develop conceptual models of regional hydrology. These community forums have identified an increase in evapotranspiration (ET) resulting from groundwater pumping for irrigation as a hypothesized mechanism of regional surface water depletion in the Wisconsin Central Sands. However, collective uncertainty exists as to the rate and magnitude of ET from potato and maize agroecosystems under different management scenarios (e.g. cover crops, tillage, irrigation).




   The goal of proposed research is to quantify the coupled water-energy balance through the groundwater-soil-plant-atmospheric continuum under different irrigation, tillage, and crop rotation schemes typical to the Central Sands using biophysical field methods. This project is conceptualized, designed, and performed with Isherwood Family Farms, a sixth-generation, 1500-acre farm with 250 acres of woodland and 7 km of stream edge located in Plover, WI, in the heart of the water-stressed region of the Wisconsin Central Sands. Field-generated estimates of groundwater recharge and ET will parameterize and validate a dynamic, agroecosystem model, Agro-IBIS, simulating hydrological responses to climate and land use changes of the past 60 years. All field and modeling results will be presented to the preexisting stakeholder network of farmers, aquatic conservationists, property owners, and policy makers in the Wisconsin Central Sands. Short-term outcomes will improve collective understanding of seasonal fluctuations of water quantity and its vulnerability to regional climate change for more informed groundwater policy. Intermediate-term outcomes will assist farmers in developing precision-irrigation strategies in order to pump and irrigate at time scales that will maximize crop productivity, minimize stress to groundwater-fed lakes and streams, and adapt to a changing climate.

Objectives/Performance Targets

The overarching goal of proposed research is to determine how agricultural land use impacts surface water quantity in the Wisconsin Central Sands in response to scientific uncertainties identified by regional stakeholders utilizing trans-disciplinary modeling and field approaches. This work will assess the impact of varied groundwater pumping, irrigation, and crop rotation schemes on groundwater discharge to surface waters in the Wisconsin Central Sands by determining coupled water-energy budgets of potato and maize agroecosystems. Field-generated estimates of ET, groundwater recharge, and biophysical fluxes will parameterize and validate a dynamic, agroecosystem model (Agro-IBIS) simulating regional surface water responses to climate and land use changes of the past 60 years. Aquatic and agricultural stakeholders will use modeling results to guide regional water policy. The specific objectives are: 


(1) Utilize monitoring wells, vadose zone lysimetry, soil moisture/temperature sensors, porometry/gas exchange, biophysical, and ecological field measurements in potato and maize cropping systems to quantify coupled water and energy budgets associated with crop type, irrigation, tillage, and cover crops.


(2) Expand, parameterize, and validate an agroecosystem model (Agro-IBIS) and link groundwater recharge to aboveground processes by capturing coupled land use, water, and energy exchange in a model that can be used at a continuum of scales from field to continent.

(3) Inform aquatic and agricultural stakeholders using modeling simulations, sensitivities, and estimates to build adaptive management plans and identify remaining areas of uncertainty/road blocks for regional water rights and land use policy.


Objective 1: We installed all vadose zone lysimetry, soil moisture/temperature sensors, and meteorological stations on Isherwood farms by the end of 2013. During the 2014, we collected these continuous measurements from six cropping systems representing Wisconsin Central Sands agricultural practices (Table 1, Figure 1). Additionally, we collected weekly measurements of stomatal conductance, drainage (below root zone), leaf area index, and canopy height/rooting depth. Additionally, we collected biweekly-monthly infrared canopy temperature data using remote sensing flights and a forward-leaning infrared camera. We plan to continue collecting these field data during the upcoming 2015 field season with the addition of photosynthesis measurements and soil cores to further parameterize our agroecosystem model.


Our initial findings suggest that there is limited groundwater recharge below irrigated cropping systems during the growing season and majority of groundwater used for irrigation in the Wisconsin Central Sands at rates similar to those applied on Isherwood Farms is consumptive (Figure 2). However, as is evident in Fig. 2, there was high spatial variability in the potential recharge measured by vadose zone lysimeters at a 1.5 m depth. This variability corresponds to subfield scale differences in topography and soil texture. For example, lysimeters 19 (sweet corn-sand), 21 (sweet corn-gravel), and 24 (field corn-gravel) are all located in relatively lower areas on their respective fields. These particular lysimeters captured much more drainage during the irrigation period than their counterparts, demonstrating that there exist localized recharge zones within agricultural fields in the Wisconsin Central Sands.


Objective 2: We have been working with 2013 and 2014 field data from Isherwood Farm to parameterize and validate an agroecosystem model (Agro-IBIS) for irrigated, sandy systems such as the Wisconsin Central Sands and also the Wisconsin Pineland Sands. We are accomplishing this task by running single cell domain simulations directly over our field sites at Isherwood Farms and using 2013 data to change model parameters.


We have successfully parameterized the irrigated maize cropping systems by “humanizing” the model’s irrigation scheme to match real soil moisture data. Agro-IBIS, like most agroecosystem models that model irrigation, triggers an irrigation event at a prescribed plant available water content (50%) and irrigates to a prescribed soil moisture content (field capacity). However, when testing both daily and annual irrigation rates against on-farm data at Isherwood farms and annual irrigation data for the Wisconsin Central Sands collected by the WI-DNR, Agro-IBIS was underirrigating (Figure 3, baseline irrigation). In order to calibrate irrigation in the model, we utilized soil moisture data from our 2013 field season and observed that 0-40 cm soil moisture data is almost always maintained at or above field capacity in order for deeper soil layers to remain moist as well. Therefore we parameterized the model to irrigate at a higher magnitude and more often until modeled 0-40 cm soil moisture data mimicked measured 0-40 cm soil moisture data (Figure 3, calibrated irrigation). Isherwood farms is considered to be a conservation-oriented farm within the region and for this reason, we observed and acknowledged that model irrigation is still lower than the WI-DNR average irrigation records for the Wisconsin Central Sands. However, in order to build stakeholder trust in the agroecosystem model, we determined that it is best to model irrigation conservatively.


Over the past year, stakeholders in the Wisconsin Central Sands have had questions about the relationship between climate change and the water budget. A specific question that they have is about the relationship between evaporative demand and irrigated agriculture (Could climate change be impacting aquatic resources?). To address this question, we implemented three potential evapotranspiration (PET) models that serve as indices of evaporative demand into the overall agroecosystem model framework. PET uses varying degrees of meteorological data to estimate the maximum potential amount of water that could leave the landscape as ET. We have been conceptualizing the irrigated agriculture water budget in the Wisconsin Central Sands as an increase from baseline rainfed agriculture to ET rates that are close to PET (that we assumed was not extremely land-cover or management specific). However, our preliminary modeling results suggest that irrigated agriculture not only changes the actual ET from the landscape (well-known), but also changes the potential ET from the landscape (Figure 4, Figure 5). 


Objective 3: We have been directly engaged with stakeholders to both inform their adaptive management efforts and better inform our field/modeling efforts. The Wisconsin Potato and Vegetable Grower’s Association established a Water Task Force (WTF) to address the problems associated with irrigated agriculture and water quantity/quality issues. The grower WTF meets monthly to discuss scientific research, listen to scientific presentations, and develop water management strategies. We have been regularly attending these meetings to share information, collaborate, and consult with growers interested in water conservation. Additionally, we worked with growers and UW-Extension scientists to develop an online assessment of baseline irrigation and water conservation practices in the Wisconsin Central Sands region in the fall of 2014. This assessment was deployed over three weeks in November 2014. As this assessment was delivered through the grower’s internal organization, participation was extremely high and 90% of growers who irrigate in Wisconsin participated in the survey representing 185,375 irrigated acres.


This survey established a baseline of irrigated cropping practices including scheduling, soil moisture monitoring, fertigation, and irrigation technology practices for the Wisconsin Central Sands. The intent is to use these baseline values to drive water conservation and reassess industry averages periodically to monitor progress.

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Impacts and Contributions/Outcomes

We presented the framework and methodology of this project at the 2014 UW Extension and WPVGA Grower Education conference in an invited talk titled, “A field-based approach for understanding changes to the water cycle and climate in the Wisconsin Central Sands.” Additionally, we presented a poster for the 2014 Wisconsin Farm Technology Days (Plover,WI) and demonstrated how to take measurements of leaf conductance at the event. We presented initial study results in an oral presentation titled, “Historical reconstruction (1948-2007) of evaporative demand in the Wisconsin Central Sands and implications for irrigated agriculture” at the American Water Resources Association’s 2015 Wisconsin Section meeting.


We plan to continue meeting and working with Wisconsin Central Sands growers to freely exchange information about this project to both improve our models of irrigated cropping systems for the region and share results with stakeholders as they become available. The growers plan to publicize results of the irrigation cropping practices survey in coming months. 


Additionally, we have had the opportunity to provide three undergraduate students with valuable research experiences through this project. In 2013, an undergrad from UW-Madison, Margaret Rice (Biological Aspects of Conservation) assisted with field studies. In 2014, two undergrads from UW-Stevens Point, Christopher Ester (Hydrology) and Amy Sandel (Water Conservation) assisted with field studies and presented a component of their work at the American Water Resources Association’s 2015 Wisconsin Section Meeting as a scientific poster.


Mallika Nocco

[email protected]
Research Assistant/Doctoral Student
Nelson Institute Center for Sustainability and the Global Environment
1710 University Avenue
Madison, WI 53726
Office Phone: 6082650572
Justin Isherwood

[email protected]
Senior Partner
Isherwood Family Farms
5911 Isherwood Rd
Plover, WI 54467
Office Phone: 7153443260
Dr. George Kraft

[email protected]
Center for Watershed Science and Education, University of Wisconsin-Stevens Point
800 Reserve St.
Rm 200
Stevens Point, WI 54481
Office Phone: 7153462984
Dr. Christopher Kucharik

[email protected]
Associate Professor
Nelson Institute Center for Sustainability and the Global Environment, University of Wisconsin-Madison Department of Agronomy
1575 Linden Drive
Madison, WI 53706
Office Phone: 6088903021