The equation of the water-energy imbalance
Abstract
The water-energy balance for a catchment over a long-term time scale describes the relationship between the components of water and energy balances of land, and actual evaporation (E) can be expressed as the function of available water (precipitation, P) and available energy (potential evaporation, Ep), i.e. the Budyko hypothesis. For a long-term time scale, the balance, which can be defined as a steady ratio of actual evaporation to precipitation (E/P), can be expected for a catchment. The balance implies an assumption that the change in water storage can be ignored. At a smaller time scale, the change in water storage (S) disturbs the balance, which leads to an imbalance. Therefore, we derive a new water-energy balance equation including the effect of water storage, which expresses actual evaporation as the function of available water (precipitation + water storage, P + S) and available energy (potential evaporation, Ep). This water balance equation was validated at different time scales (from monthly to daily) based on data from the flux observation at the Weishan experiment station in China and the Yakutsk experiment station in Russia. As mentioned in this study, there are two water-energy balance equations, namely the equation at long-term time scale (equation 1) and the equation at smaller time scales (equation 2). Equation 1 implies a stabilized relationship between E/P and Ep/P at long-term time scale, i.e. a balance. However, at smaller time scales, the relationship is not stabilized, i.e. an imbalance. Instead, equation 2 proposed a new balance, a stabilized relationship between E/(P+S) and Ep/(P+S).
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.H53E1464Y
- Keywords:
-
- 1836 HYDROLOGY / Hydrological cycles and budgets;
- 1847 HYDROLOGY / Modeling