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Title: Spatial and diurnal below canopy evaporation in a desert vineyard: measurements and modeling

item KOOL, DILIA - Ben Gurion University Of Negev
item BEN-GAL, ALON - Agricultural Research Organization Of Israel
item AGAM, NURIT - Ben Gurion University Of Negev
item SIMUNEK, JIRKA - University Of California
item HEITMAN, JOSHUA - North Carolina State University
item Sauer, Thomas
item LAZAROVITCH, NAFTALI - Ben Gurion University Of Negev

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2014
Publication Date: 7/30/2014
Citation: Kool, D., Ben-Gal, A., Agam, N., Simunek, J., Heitman, J.L., Sauer, T.J., Lazarovitch, N. 2014. Spatial and diurnal below canopy evaporation in a desert vineyard: measurements and modeling. Water Resources Research. doi: 10.1002/2014WR05409.

Interpretive Summary: Evaporation from the soil surface can be a significant loss of water in arid climates where irrigation is neccesary to grow crops. In order to improve water use efficiency, it is important to know how much water evaporates from the soil surface in order to find ways to reduce this loss. In this experiment evaporation was measured in a drip-irrigated vineyard in Israel. Small soil cores and pans of water were placed across vineyard rows to measure how evaporation changed with row position. A computer model was used to simulate the results. The measurements showed that, even though there was more light and higher temperature between the vine rows, there was very little water so evaporation was low. Evaporation below the vines, where the soil was wet from the drip irrigation, had higher evaporation but the amount of evaporation was limited due to shading by the vines. The computer model was able to simulate and confirm the measurments. This research is important to scientists, managers, and growers interested in improving water use efficiency in irrigated, arid climates.

Technical Abstract: Evaporation from the soil surface (E) can be a significant source of water loss in arid areas. In sparsely vegetated systems, E is expected to be a function of soil, climate, irrigation regime, precipitation patterns, and plant canopy development, and will therefore change dynamically at both daily and seasonal time scales. The objectives of this research were to quantify E in an isolated, drip irrigated vineyard in an arid environment and to simulate below canopy E using the HYDRUS-2D/3D model. Specific focus was on variations of E both temporally and spatially across the inter-row. Continuous above canopy measurements, made in a commercial vineyard, included evapotranspiration, solar radiation, air temperature and humidity, and wind speed and direction. Short-term intensive measurements below the canopy included actual and potential E and solar radiation along transects between adjacent vine rows. Potential and actual E below the canopy were highly variable, both diurnally and with distance from the vine-row, as a result of shading and distinct wetted areas typical to drip-irrigation. While the magnitude of actual E was mostly determined by soil water content, diurnal patterns depended strongly on position relative to the vine-row due to variable shading patterns. HYDRUS-2D/3D successfully simulated the magnitude, diurnal patterns, and spatial distribution of E, including expected deviations as a result of variability in soil saturated hydraulic conductivity.