Integration of modern space and ground RS techniques for monitoring and modelling of subsurface water fluxes

Background

Hydrological fluxes in semi-arid and arid conditions are extremely variable in time and space. Recent research outcomes (also ITC ongoing research in Botswana and Spain) indicate, that approximate stationary groundwater management models and transient models based on widely used (in Europe and Northern America) routine of temporal recharge (R) and subsurface evapotranspiration (ETs) flux averaging, substantially misleads the groundwater balance calculation and predictions in semi-arid and arid climatic conditions (Lubczynski 2000). Moreover the techniques leading to aquifer description and parameterisation are either expensive (investigation boreholes) or ambiguous and non-unique like standard geophysical methods (geoelectric, electromagnetic etc).

It is proposed to have a modern remote sensing contributions integrating space and ground techniques, allowing for new improved data acquisition schemas and improved and therefore more reliable spatio-temporal hydrological analysis. Combination of multisource space [SI (Satellite Images) and airborne data (Aerial Photographs, Radar Images)] with ground remote sensing [ADAS, Automatic Data Acquisition Systems) techniques allows obtaining the required R and ETs at demanded (by the models) spatial and temporal resolution. For spatial aquifer description and parameterisation, an integration of new Magnetic Resonance Sounding (MRS) method with other standard geophysical methods is proposed. The MRS suitability in contribution to temporal R and ETs will be investigated as well. The scheme on the next page shows the methodology described above.

Linked with setting up of hydrological monitoring networks for subsurface water balance studies, a thorough and long-term study is proposed in two study areas, in Botswana and Portugal various hydrotope characteristics.

The primary project interest focuses on Botswana area with semi arid conditions, characterized by, highly temporally and spatially variable rainfall and subsurface fluxes, deep plant rooting systems, thick water capacitive unsaturated zone, highly heterogeneous and fractured sandstone aquifer with strategically important groundwater resources being the main source of water supply in Botswana.

The second selected area in Alentejo province in Portugal has similar climatic conditions as in Botswana, intense tree transpiration and strategic groundwater importance but shallower aquifer composed of unconsolidated and secondary porosity rocks recharged not only from rainfall but also substantially from stream channels.

Within the framework of the proposed study various time dependent spatial patterns of R and ETs as well as temporally independent aquifer parameter distributions will be incorporated, calibrated and verified in a number of comprehensive transient groundwater models. After transient model calibration and verification, guidelines regarding sustainability and climate influence upon the mechanism of renewability and depletion of groundwater resources will be formulated.

Objectives

The overall work is proposed in the three packages as following:

-	Tree transpiration mapping by up-scaling of Sap flow measurements using high resolution optical and radar RS images;

-	Subsurface characterization and parameterisation with MRS and other techniques;

-	Integration of hydrological ADAS monitoring with RS and groundwater modelling for improved determination of effective groundwater recharge spatially and temporally.