Linking evapotranspiration seasonal cycles to the water balance of headwater catchments with contrasting land uses. Issue 12 (22nd December 2022)

• Record Type: Journal Article
• Authors: Peixoto Neto, Alberto M. L.; Cartwright, Ian; Silva, Marcela R. F.; McHugh, Ian; Dresel, P. Evan; Teodosio, Bertrand; Jovanovic, Dusan; McCaskill, Malcom R.; Webb, John; Daly, Edoardo
• Is Part Of: Hydrological processes. Volume 36:Issue 12(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-12-22
• Subjects: catchment water balance -- ephemeral streams -- evapotranspiration -- groundwater -- intermittent rivers -- pasture -- plantation -- recharge; Hydrology -- Periodicals; Hydrology -- Research -- Periodicals; Hydrologic models -- Periodicals; Hydrological forecasting -- Periodicals; 631.432
• DOI: 10.1002/hyp.14784
• Languages: English
• ISSNs: 0885-6087

Abstract

Abstract: Land use affects evapotranspiration rates and is a primary driver of the catchment water balance. The water balance of two catchments in southeastern Australia dominated by either grazed pasture or blue gum ( Eucalyptus globulus ) plantation was studied, focusing on the patterns of evapotranspiration (ET) throughout the year. Rainfall, streamflow, and groundwater levels measured between 2015 and 2019 were combined to estimate annual ET using a water balance equation. In the pasture, eddy covariance was used to measure ET from the catchment. Sap flow measurements were used to estimate tree transpiration in May 2017–May 2018 and Feb 2019–Feb 2021 in two different plots within the plantation. The tree transpiration rates were added to interception, estimated as a percentage of annual rainfall, to calculate ET from the plantation catchment. ET in the pasture showed strong seasonal cycles with very low ET rates in summer and ET rates in spring that were larger than the transpiration rates in the plantation, where trees transpired consistently throughout the year. The estimated annual ET from the water balance equation was comparable to ET estimated from other measurements. In the pasture, ET on average accounted for 88% of annual rainfall, while ET in the plantation was on average 93% of rainfall, exceeding it in the years with annual rainfall lower than about 500 mm. The difference between the ET rates in the plantation and the pasture was approximately 30–50 mm y −1 . The larger ET rates in the plantation were reflected in a gradual decrease in the groundwater storage. The larger ET rates were enough to cause a decrease in groundwater storage in the plantation but not in the pasture, where groundwater levels remained stable. Abstract : (a) 10‐day moving average of evapotranspiration in a pasture and tree transpiration in an adjacent catchment dominated by a plantation of E. globulus . There is a strong seasonal cycle of evapotranspiration in the pasture catchment, while the plantation catchment is overall less responsive, with transpiration rates being sustained throughout seasons. (b) Total annual rainfall below about 500 mm may trigger an imbalance in the hydrological budget, with negative effects on groundwater storage especially in the plantation.