A hydrometeorological model for basin‐wide seasonal evapotranspiration

Abstract

Abstract. A new methodology is proposed to capture the seasonal behavior of evapotranspiration from precipitation and streamflow data and to develop hydrometeorological evapotranspiration models tailored for each basin. The water budget method for determining evapotranspiration is downscaled to periods between 15 and 160 days that occur between well-marked hydrological recessions. Using these uneven time periods, the error associated with the unknown soil moisture storage is minimized, whereas groundwater storage changes are estimated by means of a classical linear groundwater reservoir whose time constant is obtained by recession analysis. This seasonal water budget (SWB) method is able to reproduce the seasonal signal of evapotranspiration even when it is absent from the precipitation and streamflow records. The estimates are also compatible with calculated monthly net radiation. By selecting short enough water budget periods it is possible to check the relationship between SWB evapotranspiration estimates and net radiation, Penman and Priestley-Taylor potential evaporation, precipitation minus outflow, water vapor deficit, and basin storage. The ratio of SWB evapotranspiration to an upper limit value represented by either net radiation or potential evaporation is well correlated with precipitation minus outflow, water vapor deficit, or both but is very poorly related to basin storage. The calculated regressions lead to a family of hydrometeorological evapotranspiration monthly (HEM) models fitted to the basins in question, in a way analogous to the calibration of rainfall-runoff models. In the two watersheds where the methodology was applied the HEM models were able to preserve mass, with total accumulated differences no larger than 0.25 mm d -• and root-meansquare errors of the order of 0.7 mm d -•. IntroductionThe calculation of reliable estimates of basin-wide evapotranspiration remains one of the most difficult questions for the science of hydrology. Still, many engineering applications of physical hydrology require evapotranspiration estimates.

Estimation of long‐term basin scale evapotranspiration from streamflow time series

“…The broader “ecological implications” is often used as one of the motivations in studies that focus on estimating watershed‐level ET [e.g., Dias and Kan , 1999; Szilagyi et al , 2007]. This can be done because of the importance of ET as an indicator of energy and mass transfer and photosynthetic activity of the catchment [ Szilagyi et al , 2007].…”

Evaluation of six empirical evapotranspiration equations - case study: Campos dos Goytacazes/RJ

“…The procedure to estimate evapotranspiration is particularly important in water budget studies to the consumptive use as required for example by ecological and water resources planning studies (Dias and Kan, 1999). Referring to agricultural production, its measurements is greatly relevant, where it is essential for determining crop water demand and consequently for designing and managing irrigation system (Gavilán, 2002, apud López-Urrea et al, 2006.…”

Water and carbon balances in a hemi-boreal forest

“…The term ∆S i represents the change in terrestrial water storage and has a great variability and uncertainty, but it is the key factor in relating terrestrial water to groundwater (Dias & Kan, 1999;Mohajerani et al, 2021). It can be subdivided in different compartments of surface water storage, as shown in equation 6.…”