|MAREK, THOMAS - Texas Agrilife Research|
|AUVERMANN, BRENT - Texas Agrilife Research|
|Evett, Steven - Steve|
|Brauer, David - Dave|
Submitted to: Agricultural Water Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2016
Publication Date: 3/1/2016
Citation: Marek, G.W., Gowda, P., Marek, T.H., Auvermann, B., Evett, S.R.,Colaizzi, P.D., Brauer, D.K. 2016. Estimating preseason irrigation losses by characterizing evaporation of effective precipitation under bare soil conditions using large weighing lysimeters. Agricultural Water Management. 169: 115-128 doi:10.1016/j.agwat.2016.02.024.
Interpretive Summary: Groundwater resources are finite and becoming increasingly scarce. Crop water use (ET) is the major use of rain and irrigation water. Irrigation scheduling using effective rainfall is used to maximize and extend these limited resources. Effective rainfall is not well defined and needed for use in field water-balance equations for effective irrigation scheduling. In this study, researchers at USDA-ARS Bushland, TX used large weighing lysimeters to determine effective rainfall from rainfall events under several ET conditions.
Technical Abstract: Irrigation scheduling is one of the most cost effective means of conserving limited groundwater resources, particularly in semi-arid regions. Effective precipitation, or the net amount of water from precipitation that can be used in field water balance equations, is essential to accurate and effective irrigation scheduling. We identified 35 precipitation events that occurred over lysimeter fields under fallow conditions in 2002, 2005, and 2009. Events were categorized into four bins of precipitation magnitude ranging from 3 mm to 35 mm. Subsequent evaporation was measured for a period up to seven days following rainfall events using large weighing lysimeters at the USDA-ARS Conservation and Production Research Laboratory in Bushland, TX. An exponential decay function was used to characterize bare soil evaporation using maximum cumulative measured evaporation (ECmax), soil water transfer constant (k), and cumulative grass reference evapotranspiration (ETCos). The considerable range of ECmax values and k values demonstrated the sensitivity of evaporative losses to antecedent soil water content and evaporative demand. We also present measured average daily evaporation values for a range of evaporative demand regimes for each precipitation bin that may provide useful information for irrigation scheduling purposes. From data analyzed in this study, for practical irrigation management applications it can be inferred that almost all of precipitation events of 10 mm and less are lost to evaporation within the following day under moderate to high ETos conditions.