The Water Balance CSCAP Speed Science Fact Sheet

Laura Bowling, Perdue University

Initial Publication Date: April 29, 2016

Summary

Fact Sheet: The Water Balance,Laura Bowling, Purdue University (Acrobat (PDF) 1.1MB Oct20 15) and additional Speed Science Fact Sheets and presentation videos are found on the SERC site and are approved for use in educational, research and extension settings. The fact sheets were developed and presented as "Speed Science" by the Climate and Corn-based Cropping Systems CAP (CSCAP).

The CSCAP is a transdisciplinary partnership among 11 institutions creating new science and educational opportunities. It seeks to increase resilience and adaptability of Midwest agriculture to more volatile weather patterns by identifying farmer practices and policies that increase sustainability while meeting crop demand.

Printable flyer >> About CSCAP Project (Acrobat (PDF) 2.9MB Oct20 15)

Learning Goals

To promote the long-term sustainability and productivity of U.S. corn-based cropping systems against recent climate trends and future uncertainty.

Project Objectives:

Develop standardized methodologies and perform baseline monitoring of carbon, nitrogen and water footprints at agricultural test sites across the Midwest.
Evaluate how crop management practices impact carbon, nitrogen and water footprints at test sites.
Apply models to research data and climate scenarios to identify impacts and outcomes that could affect the sustainability and economic vitality of corn-based cropping systems.
Gain knowledge of farmer beliefs and concerns about climate change, attitudes toward adaptative and mitigative strategies and practices, and decision support needs to inform the development of tools and practices that support long-term sustainability of crop production.
Promote extension, outreach and stakeholder learning and participation across all aspects of the program.
Train the next generation of scientists, develop science education curricula and promote learning opportunities for high school teachers and students.

Context for Use

For formal and informal education. This publication for farmers, farm advisors and agricultural teachers contains articles about some of the findings of a USDA-NIFA-funded project researching ways to make corn-soybean systems more resilient to the impacts of climate change.

Description and Teaching Materials

Printable handout pdf >> Fact Sheet: The Water Balance,Laura Bowling, Purdue University (Acrobat (PDF) 1.1MB Oct20 15)

The water balance is the statement of the conservation of mass within the hydrologic or water cycle, where a change in internal moisture storage is balanced by moisture fluxes into and out of an area of interest. Overlong, stationary time periods, that is, multi-year periods with little to no change in the mean behavior of the hydrologic system, the field-scale water balance describes how precipitation results in fluxes such as surface runoff, drainflow, groundwater recharge and evapotranspiration. The mean annual water balance is an essential tool both for estimating components that cannot be measured directly (e.g. groundwater recharge) and for validating field measured values (e.g. is measured annual drainflow less than annual precipitation).

Evapotranspiration represents the largest outflow component of the long-term water balance, approximately 2/3rds of precipitation, but it is also one of the most difficult to measure. The watershed-scale is the fundamental scale for water balance calculations, since lateral outflow components, including surface runoff, drainflow and groundwater discharge can be captured at one streamflow monitoring location. During periods of change (non-stationarity) due to short time variations (e.g., seasonal differences in precipitation), or long term environmental changes, the change in storage terms that balance the inflow and outflow terms become more important. For example, increasing precipitation intensity can result in the generation of more surface runoff, decreasing the positive change in soil moisture associated with rainfall events. Storage of snow and soil ice decreases during warmer winter periods, increasing winter surface runoff, drainflow and groundwater recharge relative to historic periods and changing historic soil moisture and temperature values at the start of the growing season. The interconnectivity of water cycle fluxes and storage terms represented by the water balance mandates a comprehensive monitoring and analysis approach to increase understanding of future agricultural water sustainability

Observed water balance data for the Davis Purdue Agricultural Center field site in December 2012, where the primary inflow term, precipitation (top), is reflected in the primary outflow term, drainflow (bottom). For an isolated field, we expect precipitation to exceed drainflow over annual intervals, but, over one hour measurement intervals, the temporary storage and release of moisture in the soil can allow drainflow rate to exceed precipitation rate.

Teaching Notes and Tips

The CSCAP project's multi-pronged approach utilizes place-based education at multiple levels (9-12, undergraduate, graduate, extension and stakeholders) to increase learning and foster a new generation of scientists, farmers, entrepreneurs and citizens.

Assessment

Assessment is at the discretion of the educator and how the Speed Science Fact Sheets are applied.

References and Resources

For more information, contact:Dr. Laura Bowling, Associate Professor, Purdue University, bowling@purdue.edu, 765-494-8051Lynn Laws, Communication Specialist, Climate and Corn-based Cropping Systems CAP, lynnlaws@iastate.edu, 515-294-7380This presentation was given at the Climate and Corn-based Cropping Systems Coordinated Agricultural Project (CSCAP)2012 Annual Meeting. This handout and supplemental video are approved for use in research, education, and extension.