TRAIN
For the regionalisation of the water balance components specific local elements (topography, land-use, soils) and varying meteorological conditions are included in the calculation process. The following elements are taken into account:
- available radiant energy fluxes, allowing for varying sunshine and shade conditions;
- data concerning different types of land-use, such as height of vegetation, leaf surface development, albedo;
- structure of the snow cover, snow-melt, and sublimation from snow;
- interception and interception evaporation according to Menzel (1997);
- transpiration through plants based on the Penman-Monteith equation (Monteith, 1965). It depends on the calculation of canopy resistances which are modified by the state of growth of the vegetation, soil moisture and weather conditions (Menzel, 1996);
- availability of water in the soil;
- groundwater recharge.
Application of TRAIN
Within the GLOWA Jordan River project, it is planned to apply and validate the model at selected sites (including both agricultural and natural vegetation) in the Jordan region, where continuous climate data series and information on soils, land-cover and individual water balance components is available. This work serves to
- further develop the model for an improved consideration of hydrological processes of semi-arid and arid environments;
- evaluate the interactions between water fluxes, vegetation and land-use under the given climatic and physiographic conditions. The investigation of the hydrological conditions during drought periods will be of special interest;
- integrate climate change scenarios into the modelling studies and extensive evaluation of the impact of projected climate change on the water balance.
For phase 2 of the project it is intended to carry out an areal analysis of the above described work, including land-use change scenarios. In any case, project work at the University of Kassel requires close collaboration with project partners and stakeholders from all affected countries.
Principal requirements for model application are daily or hourly data of the following climate parameters:
- precipitation;
- solar radiation (alternatively: sunshine duration or net radiation);
- air temperature;
- relative humidity;
- wind speed.
Ideally, model application will be carried out for all climate characteristics within the Jordan watershed, including arid conditions or regions with a periodic / episodic presence of snow. Output data of the TRAIN model are available in the same temporal resolution (daily / hourly) as the climate input data and include:
- the storage of intercepted water within the canopy and interception evaporation;
- transpiration;
- soil evaporation;
- snow accumulation and snow melt;
- the soil moisture status;
- groundwater recharge.
The following graph summarises the input requirements and the simulated processes / the modelled output by means of the TRAIN model.
Figure 1: Overview of the TRAIN model, its input parameters / the pre-processing of input data (shaded box), the simulated processes and related output data.