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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.

A construção de represas pode aumentar a emissão de gases do efeito estufa (GEE), principalmente metano (CH4) pela decomposição anaeróbica dos resíduos florestais, como galhos, ramos, folhas e miscelânea inundados. Objetivou-se, neste estudo, avaliar a emissão de CH4 após a inundação do solo coberto com resíduos florestais. Unidades experimentais foram construídas com tubos de PVC contendo solo e diferentes combinações de dose (0; 21,2; 42,3 e 64,1 Mg ha-1) e tipo de resíduos (folhas, ramos e miscelânea, galhos e composição original) e água de rio. O delineamento experimental foi inteiramente casualizado com arranjo fatorial e três repetições. As taxas de emissão de CH4 foram monitoradas em 19 eventos durante um ano (Fevereiro/2012 a Março/2013). Cerca de 75 dias após a incubação do solo com resíduos florestais verificou-se aumento das emissões de CH4, ocorrendo dois picos de emissão, aos 111 e aos 249 dias. A emissão acumulada de CH4 no primeiro ano de alagamento foi de 200 g C m-2 na dose zero, passando a valores próximos a 400 g C m-2 nas doses de 21,2 Mg ha-1 e maiores, não havendo efeito do tipo de resíduo, apenas da dose, como fator isolado.