Modelling the non‐linear hydrological behaviour of a small Mediterranean forested catchment

Abstract

Abstract:A progressive perceptual understanding approach was used to identify a model structure able to represent the non-linear behaviour of the hydrological cycle in a small intermittent Mediterranean stream. The initial lumped model structure consisting of a series of four connected water tanks (LU3) progressed to a model with five tanks (LU4), and finally to a semidistributed model structure (SD4) in which spatial variability of the evapotranspiration according to the vegetation cover and to the local aspect was considered. In the final model structure, which gave the best fit (Nash-Sutcliffe efficiency index D 0Ð78), an additional tank representing the riparian zone was included (SD4-R). Results showed that the abrupt changes of the riparian water table during summer and the formation of a perched water table during the transition from dry to wet conditions were the main mechanisms leading to the non-linear hydrological behaviour. The transpiration process from the saturated zone and the spatial variability of evapotranspiration resulted in key factors successfully representing the annual water balance. The spatial and temporal validations carried out for each of the four model structures considered in this study supported the hypothesis adopted during the calibration process.

The impact of poplar tree plantations for biomass production on the aquifer water budget and base flow in a Mediterranean basin

“…This dual dynamic water flux between the aquifer and the stream has been observed in Mediterranean riparian zones where the riparian vegetation induces infiltration from the river to the aquifer and reduces the flow from the aquifer to the river (Medici et al, 2008;Mencio et al, 2014).…”

Regional parent flood frequency distributions in Europe – Part 2: Climate and scale controls

“…Aside from precipitation input, other catchment processes can also play an important role in shaping the properties of the flood distribution. The presence of non-linearities in runoff production and routing in smaller, drier basins (Medici et al, 2008) in contrast to the aggregation of processes in larger catchments (Sivapalan et al, 2002) will translate in decreasing values of L-Cv and L-Cs with increasing values of MAP and, more strongly, catchment size. One visible consequence of the higher dispersion and skewness of the flood frequency distributions with decreasing catchment area and increasing aridity is the fact that predicting flood magnitudes and exceedance probabilities in ungauged basins is more difficult in smaller, more arid catchments, as compared to bigger, less arid ones (see e.g.…”

Modelling the inorganic nitrogen behaviour in a small Mediterranean forested catchment, Fuirosos (Catalonia)

“…3. The hydrological conceptual scheme adopted for the semi-distributed model differs slightly from that published in Medici et al (2008). In this case, part of the hillslope discharge (corresponding to the area not drained by the four small reservoirs, which represents approximately 37% of the total catchment area) is routed through the riparian storage before reaching the stream channel (Fig.…”

“…In a next phase of development, the LU4-R-N was extended to include the spatial variation in evapotranspiration and lithology (SD4-R-N). As such, the catchment was divided into 4 HRUs: the three main catchment lithological units (leucogranite, granodiorite and sericitic schists, all together cited in this paper as hill-slope zone) and the riparian zone, as those used in the application of the SD4-R hydrological model (Medici et al, 2008). Thus, the PET spatial variability for the actual evapotranspiration computation was included taking into account the representative vegetation cover and the potential sunshine arriving to each lithological unit according to its representative aspect and surrounding relief.…”

“…Namely, these new elements are: biological thresholds responses to soil moisture in order to reproduce the pulse dynamic observed in such environment; a specific function for the soil moisture correction factor for the mineralization process; nitrification and denitrification processes associated to the shallow perched water table and finally, the introduction of a riparian zone compartment. The nitrogen model scheme developed in this study was coupled to already existent hydrological conceptual models previously applied to the Fuirosos catchment (Medici et al, 2008).…”