Modelling the impacts of land-cover change on streamflow dynamics of a tropical rainforest headwater catchment

Abstract

A modelling experiment is used to examine different land-use scenarios ranging from extreme deforestation (31% forest cover) to pristine (95% forest cover) conditions and related Payment for Ecosystem Services (PES) schemes to assess whether a change in streamflow dynamics, discharge extremes and mean annual water balance of a 73.4-km 2 tropical headwater catchment in Costa Rica could be detected. A semi-distributed, conceptual rainfall-runoff model was adapted to conceptualize the empirically-based, dominant hydrological processes of the study area and was multi-criteria calibrated using different objective functions and empirical constraints on model simulations in a Monte Carlo framework to account for parameter uncertainty. The results suggest that land-use change had relatively little effect on the overall mean annual water yield (<3%). However, streamflow dynamics proved to be sensitive in terms of frequency, timing and magnitude of discharge extremes. For low flows and peak discharges of return periods greater than one year, land use had a minor influence on the runoff response. Below these thresholds (<1-year return period), forest cover potentially decreased runoff peaks and low flows by as much as 10%, and non-forest cover increased runoff peaks and low flows by up to 15%. The study demonstrated the potential for using hydrological modelling to help identify the impact of protection and reforestation efforts on ecosystem services.Key words ecosystem services; PES; hydrological modelling; tropics; Costa Rica; land-use change Modélisation des effets du changement de couvert végétal sur la dynamique des débits d'un bassin versant amont en forêt tropicale humide Résumé Cet article utilise une expérience de modélisation pour examiner différents scénarios d'occupation des sols allant de la déforestation extrême (couverture forestière à 31%) aux conditions d'origine (couverture forestière à 95%), et les schémas associés de Paiement pour les Services Ecosystémiques (PSE) afin de déterminer si un changement de dynamique de l'écoulement fluvial, des extrêmes de débit et du bilan hydrique annuel moyen, peut être détecté dans un bassin versant amont tropical de 73,4 km 2 au Costa Rica. Un modèle conceptuel pluiedébit semi-distribué a été adapté pour conceptualiser les processus hydrologiques dominants de la zone d'étude, déterminés de façon empirique. Il a été calé sur plusieurs critères, à l'aide de différentes fonctions objectif et de contraintes empiriques sur les simulations du modèle, dans le cadre d'une approche de Monte-Carlo pour tenir compte de l'incertitude sur les paramètres. Les résultats suggèrent que le changement d'occupation des sols a eu peu d'effet sur le rendement en eau annuel moyen (<3%). Toutefois, la dynamique des débits se montre sensible en termes de fréquence, de temporalité et d'ampleur des débits extrêmes. Pour les faibles débits et les débits de pointe de périodes de retour supérieures à un an, le changement d'utilisation des sols a eu une influence mineure sur la réponse en d...

Earthworms and tree roots: A model study of the effect of preferential flow paths on runoff generation and groundwater recharge in steep, saprolitic, tropical lowland catchments

“…The effective percolating VPFP number, the mean and standard derivation of the VPFP diameter were all important in determining the overall runoff and base flow generation, seen from Figures c, f, and i that the R b /R values increased accordingly with the increase in both the VPFP number and size. The fact that all the R b /R values were larger than 70% indicated the large contribution of groundwater storage to streamflow, which was consistent with the results from other studies in tropical catchments [ Birkel et al ., ; Ogden et al ., ]. Maximum values of NSE log (Figures b, e, and h) were observed in relation to every VPFP parameter, which mainly corresponded to the values we estimated based on field observations and literature as discussed earlier.…”

Spatially distributed tracer‐aided modelling to explore water and isotope transport, storage and mixing in a pristine, humid tropical catchment

“…Tropical headwater catchments often have volcanic origins and exhibit stratified volcanic rocks and soils overlying steep terrain; hence, they are subjected to a complex suite of nonlinear and preferential hydrological processes. Generic conceptual models used to predict streamflow in humid tropical catchments include, among others, HBV‐light (Beck et al, ; Birkel, Soulsby, & Tetzlaff, ) and TOPMODEL (Campling, Gobin, Beven, & Reyen, ; Moličová, Grimaldi, Bonell, & Hubert, ), both showing good prediction performance but a limited capability to assess streamflow sources. More physically based and complex models such as soil and water assessment tool (SWAT) were also widely applied for simulating hydrologic behaviour of tropical catchments (Pereira, Martinez, Pruski, & da Silva, , for an example from Brazil).…”

Interactions between payments for hydrologic services, landowner decisions, and ecohydrological consequences: synergies and disconnection in the cloud forest zone of central Veracruz, Mexico

“…This near-neutral result was attributed to the combined compensatory effect of a lower ET for pasture (leading to higher flows) and a comparatively small difference in CWI for cloud forest versus aerodynamically rough pasture (lower under the latter, leading to reduced flows). Another modeling-based study conducted in a cloud forest region in central Costa Rica also found that while conversion of catchments from primarily forest to pasture had relatively little effect on mean annual water yield (< 3%), forested catchments had lower runoff peaks and higher dryseason flows by up to 10% on short time scales (< 1-year return period) (Birkel et al 2012). This ability of forests to provide protection was not maintained for large return interval floods (< 1-year return period).…”