Fleischbein, K. (2004): <b>Wasserhaushalt eines Bergwaldes in Ecuador: experimenteller und modellhafter Ansatz auf Einzugsgebietebene</b> Justus-Liebig-University Giessen, <i>phd thesis</i>
Resource Description
Title:
Wasserhaushalt eines Bergwaldes in Ecuador: experimenteller und modellhafter Ansatz auf Einzugsgebietebene
Short Name:
ECSF-Wasserhaushalt
FOR816dw ID:
1028
Publication Date:
2004-10-15
License and Usage Rights:
Resource Owner(s):
Individual:
Katrin Fleischbein
Contact:
email:
webmaster <at> tropicalmountainforest.com
Abstract:
The understanding of the hydrological functioning of a tropical ecosystem allows to evaluate the consequences of a changed land use.<br/>
On the east-facing slope of the Andes in Ecuador between 1900 and 2150 m a.s.l. I studied the above- and belowground driving variables of the water budget. The objectives were to determine the elements of the water budget experimentally and with an optimized model and to elucidate the hydraulically relevant processes along five 20 m-long transects in three 8-13 ha-large microcatchments under montane rain forest.<br/>
Water fluxes were weekly measured between April 1998 and April 2001, the mean annual evapotranspiration was calculated with a budget approach. For the canopy, I determined the water storage capacity and assessed the influence of the vegetation density and epiphyte coverage on interception and canopy evaporation of the precipitation. The vegetation density was approximated by the leaf area index [LAI] and the fraction of the precipitation falling through gaps of the canopy. In addition, I modeled throughfall and stemflow by adapting the analytical canopy model of Gash. In the soil, I determined the saturated hydraulic conductivity and the water contents. To calculate the reaction of surface flow on precipitation events and to identify the soil processes controlling the surface flow, I compared a ?black box? (NAMOD) with a ?semi-empirical? (TOPMODEL) model approach.<br/>
The mean water storage capacity of the dry leaves is 1.91±1.94 mm and that of the trunks 0.041±0.02 mm. The LAI ranges from 5.2 to 9.3. Epiphytes - mainly mosses - cover up to 80% of the trunk and branch surfaces. The fraction of precipitation falling through gaps of the canopy correlates significantly with the interception loss (r = -0.77, n = 40). During dry periods the mosses and lichens tend to decrease the water storage capacity of the trunks.<br/>
The saturated hydraulic conductivity decreases drastically at the border between organic layer and mineral soil where it was highly variable. The high stone content of, on average, 40Vol.% has a substantial effect of the flow regime. Based on the results of the precipitation-surface flow modeling the hydraulically effective soil layer can be separated into two water reservoirs (organic layer and mineral soil). The water flow in the soil occurres rapidly in lateral direction in the organic layer and/or much slower, mainly vertically in the deeper mineral soil layers. Water flow in the latter soil layers during strong rain events is little likely, because the organic layer is rapidly saturated favoring interflow.<br/>
The weekly surface flow measurements result in an overestimation of the annual water output from the catchments because high flow events were overrepresented. The mean annual surface flow in the three catchments, calculated on the basis of daily modeled flow rates, ranges between 27 and 46% of the precipitation. The annual evaporation, calculated on the basis of daily surface flow rates, ranges between 1281 and 1889 mm, i.e. 54-73% of the precipitation.<br/>
My results demonstrate that rapid lateral water flow in the organic layer of the soil dominates the flow regime. The destruction of the forest and removal of the organic layer would result in soil erosion and increased intensity of high-flow events.
