Consumptive use and return flows in urban lawn water use

Research was conducted to estimate grass consumptive use and return flow (deep percolation) in urban lawn water use. Two types of small lysimeters were used - a drainage-type lysimeter of 40 cm diameter and 60 cm depth and a weighing-type lysimeter of 30 cm diameter and 60 cm depth. A large hydraulic weighing-type lysimeter of 1 [m.sup.2] surface area and 1.3 m depth was used as the reference for comparison. The amount of water application, deep percolation, and change in soil moisture content were measured for the 1992-1994 summer seasons, and evapotranspiration (ET) was calculated using a volume balance equation. The results suggest that the small lysimeters are of acceptable accuracy compared to large lysimeters for estimating evapotranspiration. The weighing-type small lysimeters appeared to be more consistent but underestimated evapotranspiration compared to the drainage-type lysimeters. The results for estimating deep percolation with the small lysimeters are not conclusive yet.