The identification of the moment when direct flow ends and baseflow begins is one of the biggest challenges of hydrological cycle modeling. The objectives of this research were: to characterize the recession curves (RC) and to separate the components of the hydrograph in a compact model. The RC were extracted from time series in three subwatersheds in Mexico. An expo-linear model was adapted and fitted to the master recession curves to find the transition point of the hydrograph and separate the baseflow. The model discriminated the RC in two decreasing ratios: one linear associated to the direct flow, and one exponential linked to the baseflow. The transition point between these two flows was obtained analytically by equaling both ratios. The derivation of a model parameter allowed to find the maximum points in the hydrometric time series, which were the criterion to separate the baseflow. The application of this model is recommended in the analysis of RC with different magnitudes from the flexibility and attachment to the fundaments of exhaustion of a reservoir.

In the perspective of Darwinian hydrology, Budyko hypotheses can be the foundation of approaches for developing models. Numerous Budyko-type models meeting established boundary conditions (water and energy limits) have been developed based on the Budyko hypothesis on the long-term-average annual mass and energy balance. Some of these models are grounded on empirical bases, while others have been formulated on sophisticated mathematical developments. We analyze the basic hypotheses underlying some Budyko-type models; we first describe some published models and then examine their underlying hypotheses in a hydrologically intuitive space (precipitation versus runoff). The analyses show that the models studied are a consequence of assuming that two parallel straight lines (of unit slope) of different intercepts are indeed equal (proportionality hypothesis). This hypothesis gives rise to different Budyko-type models that, although mathematically correct and meeting the limits (partially) related to the Budyko hypotheses, do not yield any information about what happens between those limits. To overcome the extreme energy limit, an expolinear model is introduced.

One of the challenges faced by subwatershed hydrology is the discovery of patterns associated with climate and landscape variability with the available data. This study has three objectives: (1) to evaluate the annual recession curves; (2) to relate the recession parameter (RP) with physiographic characteristics of 21 Mexican subwatersheds in different climate regions; and (3) to formulate a Baseflow (BF) model based on a top-down approach. The RP was calibrated utilizing the largest magnitude curves. The RP was related to topographical, climate and soil variables. A non-linear model was employed to separate the baseflow which considers RP as a recharge rate. Our results show that RP increases with longitude and decreases with latitude. RP displayed a sustained non-linear behavior determined by precipitation rate and evapotranspiration replace the P/E parts with \(\frac{P}{E}\) over years and subwatersheds. The model was fit to a parameter concurrent with invariance and space-time symmetry conditions. The dispersion of our model was associated with the product of replace the P/E parts with \(\frac{P}{E}\) by the aquifer’s transmissivity. We put forward a generalized baseflow model, which made the discrimination of baseflow from direct flow in subwatersheds possible. The proposed model involves the recharge-storage-discharge relation and could be implemented in basins where there are no suitable ground-based data.

Los ecosistemas terrestres tienen almacenes en la biomasa aérea (B) de alta importancia para acciones de mitigación del cambio climático a través de mecanismos tales como REDD+. Para obtener posibles compensaciones financieras por evitar deforestar o degradar los bosques, además de la conservación, incrementar los almacenes de carbono y manejo forestal sustentable, es necesario evaluar los errores de estimación de biomasa y carbono, que generalmente están asociados al modelo alométrico usado. Los modelos alométricos sobre las relaciones entre diámetro normal (D) y altura total (H) con la biomasa usan técnicas estadísticas que no aprovechan las relaciones entre los parámetros de los modelos, ni las relaciones entre las constantes y exponentes de cada modelo, por lo que en este trabajo se presenta un marco teórico generalizado aplicable a nivel de monoespecies y multiespecies, el cual fue aplicado a un conjunto de 684 mediciones de D, H y B, provenientes de 23 bases de datos de especies individuales. Los resultados obtenidos, cuando se cuenta con datos, prácticamente no presentaron error cuando se consideraron todos los parámetros. Cuando faltó información de un parámetro, las estimaciones reali­zadas con diferentes aproximaciones mostraron errores de estimación comparables con los obtenidos por los métodos clásicos de generación de modelos alométricos generalizados. El proceso metodológico desarrollado sirve de base para plantear cambios en los enfoques de generación de información alométrica, para simplificar modelos y para reducir los errores en la estimación de la biomasa y el carbono.

Waterbody evaporation (E) within endorheic basins in semiarid areas is critical in determining the water balance. Accurate E measurements can provide valuable information for the sustainable management of water resources in the face of climate change scenarios. However, evaporation can be estimated through methods as efficient as Penman using variables from agroclimatic stations, such as wind velocity, net radiation, relative humidity, and air temperature, which have spatiotemporal variability. Within the evaporation models based on remote sensing (RS) is the surface energy balance model (SEB), which has been applied to different methodologies and extends the measurements of evapotranspiration (ET) at a regional level. SEB-based methodologies use physical principles with minimal weather data requirements to estimate ET. Hence, this article compares two RS methodologies that estimate evaporation: The Regional Evapotranspiration Estimate Model (REEM) and the Earth Engine Evapotranspiration Flux (EEFlux). Comparing ET measurements obtained from REEM and EEFlux for seven Landsat OLI scenes in the agriculture cycle of April to September applied against the simplified Penman equation showed that the REEM performed better (d = 94 %) than the EEFlux (d = 68 %) for the indicated period. Although the comparison of REEM and EEFlux shows accurate E measurements (REEM), gridded weather data (EEFlux) needs to improve, increasing the scale using local information.