Measuring and modeling soil water budgets

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Water is our most precious resource. This research program will advance knowledge on measuring and modeling water flow and contaminant transport through field soils under different agricultural management practices and climatic regimes. The research results will be of significant interest to farm commodity groups, government agricultural research scientists and engineers, and others managing and studying soil water and groundwater resources in rural areas. The results could be used to predict least-impact timing of nutrient and manure applications, irrigation timing and amount, design of drainage systems to minimize groundwater contamination, etc. The main objectives of the research program are to develop new methods of measuring and modeling temporal variability of soil hydrologic properties under different agricultural management practices and climatic regimes, calibrate and validate new models using the field data, and develop a database of long-term soil water balances for different regions of Canada. A combination of instrument development, fieldwork and computer modeling will be used to fulfill the objectives. The first step is to develop novel methods of automatically and continuously measuring soil hydrologic properties in the field using multipurpose soil water sensors. The field data will be used to calibrate and test a new model that estimates the soil water balance using crop, climatic and soil hydrologic property data as main inputs. The new model will include factors critical to many Canadian agricultural regions such as the effects of freezing and thawing, tile drainage, and temporal variability of soil hydrologic properties on the estimated soil water balance. Even in today's most sophisticated water balance simulation models, allowing for the effects of changes in soil hydrologic properties during the growing and non-growing seasons is currently unavailable. Temporal variability in soil hydrologic properties may be even more important than spatial, but it has received relatively little attention. As a long-term goal, the database of model estimated evapotranspiration, deep drainage, and runoff for different cropping systems and regions in Canada will be made available to the public on the Internet.