MODELLING ENVIRONMENTAL CONDITIONS AND WATER BUDGET DURING LITTLE ICE AGE

The Cañada Hermosa is a graben structure in the semi-arid SE Spain, located in the the Upper Rio Guadalentin watershed. In this area during Holocene huge fan complexes were deposited. Sediments extracted from one of these fans were analyzed on overall sedimentological parameters and on chemical composition. Using these information as paleoenvironmental indicators, supplemented by radio carbon data Holocene paleoenvironmental development of the Cañada Hermosa was outlined. It is shown that environmental conditions during late glacial were humid but that strong aridification characterizes the change to the Holocene. Only during the climatic pessimum of the Little Ice Age a slightly increased humidity, coinciding with increasing weathering rates was determined. Parallel, for the catchment of the Upper Rio Guadalentin actual water balance was modelled using the conceptional distributed TOPMODEL approach. Input data necessary were a DEM, land use and soil data, meteorological and discharge data. To characterize the actual water budget conditions potential evaporation was computed on a cell-by-cell basis. Based on this the interception was calculated following a simple bucket approach. The infiltration model devides the precipitation in infiltration surplus, including surface runoff and in infiltrating water, which is directed into the soil. The tendency of water storage in the soil matrix is expressed by the saturation deficit. The formation of baseflow, interflow and surface runoff is controlled by the soil storage concept and was calculated separately forming the overall discharge. Based on the information obtained from the proxy-data scenarios of environmental conditions during period of Little Ice Age were developed. While climate conditions were derived from proxy-data, land use data about the second half of the 19th century were available from written sources. The increased humidity during Little Ice Age was attributed to a) increased rainfall during summer, b) increased rainfall during winter. Development of scenarios first included qualitative reconstruction of environmental conditions. After that, data sets were produced to be implemented into the water balance model. Thus, maps visualizing climatic conditions as well as water balance character during Little Ice Age were produced.