A soil water balance model for a rain-fed vineyard in a micro catchment based on dual crop coefficient

Abstract

This paper describes a soil water balance model for a rain-fed vineyard in micro catchment water harvesting system based on dual crop coefficient to separate actual crop transpiration and soil evaporation in the Bajgah area, Fars Province, I. R. of Iran. In this model, root depth was divided into seven layers each with 20 cm thickness, and includes rainfall, run-off, actual transpiration, soil evaporation, water contribution from deeper layers and deep percolation. In this study, 10 micro catchments containing a grapevine tree with an area of 13.4 m² were built in the study area and volumetric soil moisture contents at a depth of 120 cm and amount of soil water at depths of 0–120 cm were measured during the growing season of 1984–1987. Then, the model was run by using weather data during these years, and the volumetric soil moisture contents in each day were estimated. The daily value of upward water contribution from deeper soil layers was considered equal to 0.72 mm. The results showed that there was no significant difference between the values of estimated and measured volumetric soil moisture contents in depth of 120 cm, and amount of soil water at depths of 0–120 cm.

Keywords:

• soil water balance
• rain-fed vineyard
• micro catchment
• dual crop coefficient
• transpiration
• evaporation