Main aim: To determine the importance of the land use / land cover on hydrological cycle components in tropical mountainous environments (TMEs), with an analysis of the spatial variability of hydrological sensitivity to land use change. To achieve this, a pair of catchments with similar characteristics (climatic, topographic, pedologic and geomorphologic) were chosen. The difference between the catchments is the land cover; one is covered by primary forest, the other largely by secondary forest and deforested areas. The catchments are on the Andean mountains at the south of Colombia, South America; They are the Tambito (750 ha) and the Palo Verde (650 ha) watersheds. In this thesis modelling will be used to understanding and predict the hydrological impact of land use change within the catchments and to determine the spatial variability in landscape sensitivity to this change.
Objectives: (1) To produce a hydrological GIS based model to monitor and simulate the impact of land use change on hydrological processes. (2) To parameterise and validate the hydrological model at the plot scale for different land uses. (3) To develop methods for parameterisation of the model at the catchment scale.(4) In order to determine the spatial variability of hydrological sensitivity to land use change, to create different scenarios of land use across the two catchments within the model, to test it and to give a concept of the importance of land use / land cover on the hydrological sensitivity.
Using a knowledge of physical processes, a hydrological model will be constructed using a Geographic Information System (GIS) framework. The model will include components for: solar radiation, evapo-transpiration, interception, infiltration, recharge, overland flow, through flow and soil erosion. The model will be tested over instrumented plots in (a) primary, (b) secondary and (c) deforested areas. Two gauging stations (in Tambito and Palo Verde Rivers), will be used in order to first of all produce the hydrological balance in the catchments and thereby validate the GIS models and secondly to determine the landscape sensitivity to land use change.
Spatial data are integrated with a GIS at 25 m pixel resolution which to date includes topography, soils and vegetation cover types. The model is developed and tested for a single grid cell (1D model) as a spreadsheet model before being implemented into the GIS (2 D model). 1 D model parameterisation and validation will be carried out at plot scale for each land use (deforested, primary and secondary forest). Parameterisation and validation in the distributed (2 D) model will be carried out at catchment scale using gauging river stations data.
These two catchments will be used as a paired catchment for comparison to achieve the objective of this thesis. The hydrological characteristics of each land use type have been sampled using plots of 20 m2. Each plot has a hydrological station collecting data that will be used for model input, with separate data for model validation. To determine vegetation biomass, leaf area index and soil properties of each the land use, an experimental plot of one ha (1 ha) will be set. Two river stations will be installed at the output of each catchment to validate the model fluxes at the catchment scale.
So far the model is implemented on the GIS and the 2D model is undergoing testing and validation procedures. It will then be applied to produce information for different land use scenarios and sensitivity analysis.
1 Cloud cover (kj) -hourly
2 Solar Radiation (Kj) -hourly
3 Net radiation (Kj) -hourly
4 Infiltration (mm/hr) -hourly
5 Hydraulic conductivity (mm/hr) - hourly
6 Matric potential (Kpa) -hourly
7 Surface runoff (mm/hr) -hourly
8 Stream flow (mm/hr) - hourly
9 Rainfall (mm/hr) -hourly
10 Erosion (mm/hr) -hourly
11 Soil moisture (mm) -hourly
12 Evaporation (mm/hr) -hourly