14 Groundwater
Allard M.J. Meijerink
International Institute for Aerospace Surveys and Earth Sciences (ITC)
PO.Box 6, Boulevard 1945, 7500 AA Enschede, The Netherlands
14.1 Introduction
Groundwater is essentially a subsurface phenomenon. The common current remote
sensing platforms record features on the surface. Most of the information for
groundwater, as yet, has to be obtained by qualitative reasoning and semiquantitative approaches. The remotely sensed information is often of surrogate
nature and has to be merged with geohydrologic data to become meaningful.
Airborne geophysics, such as aeromagnetic surveys, can provide subsurface
information (Reeves 1992) but the data has to be interpreted because non-unique
solutions may be possible. Non-ground based micro-wave sensors have some
capability of penetration, but practical results may be obtained only if the
conditions are right, i.e. coarse grained materials, simple geology and fairly
shallow groundwater table. It is true that in certain areas rather spectacular
microwave imagery has been produced, displaying partly buried fossil drainage
networks in a desert (McCauley et al.,1982) or fracture patterns on thermal
infrared imagery (Warwick et al.,1979). However, such imagery are incidental.
This text is written with practical applications in mind and the use of remote
sensing is discussed and illustrated according to a general method of assessing
regional groundwater resources, which starts with:
Conceptualization of the hydrogeology, which consists of building-up the
three dimensional hydrogeological setting based on surface and subsurface
geology, followed by estimation of the regional groundwater surface. After
that the conceptual groundwater model can be expanded by the identification
of flow systems, in particular intake areas and zones with groundwater
discharge.
Water budget. Once the conceptual model is completed, in the sense that all
the available information, geologic, water table and base flow data has been
considered, the usej of remote sensing for the upper boundary condition is
discussed, namely recharge, evapotranspiration loss and estimation of water
use for irrigation from groundwater.
Quite some space is devoted to the recharge for two reasons: (1) Remote sensing
offers unique possibilities in assessing the spatial patterns, and (2) Groundwater is
or is becoming a scarce resource in quantity and quality and this resource can be
influenced by the conditions near the surface, in particular by the land cover and
G. A. Schultz et al. (eds.), Remote Sensing in Hydrology and Water Management
© Springer-Verlag Berlin Heidelberg 2000
Allard M.J. Meijerink
International Institute for Aerospace Surveys and Earth Sciences (ITC)
PO.Box 6, Boulevard 1945, 7500 AA Enschede, The Netherlands
14.1 Introduction
Groundwater is essentially a subsurface phenomenon. The common current remote
sensing platforms record features on the surface. Most of the information for
groundwater, as yet, has to be obtained by qualitative reasoning and semiquantitative approaches. The remotely sensed information is often of surrogate
nature and has to be merged with geohydrologic data to become meaningful.
Airborne geophysics, such as aeromagnetic surveys, can provide subsurface
information (Reeves 1992) but the data has to be interpreted because non-unique
solutions may be possible. Non-ground based micro-wave sensors have some
capability of penetration, but practical results may be obtained only if the
conditions are right, i.e. coarse grained materials, simple geology and fairly
shallow groundwater table. It is true that in certain areas rather spectacular
microwave imagery has been produced, displaying partly buried fossil drainage
networks in a desert (McCauley et al.,1982) or fracture patterns on thermal
infrared imagery (Warwick et al.,1979). However, such imagery are incidental.
This text is written with practical applications in mind and the use of remote
sensing is discussed and illustrated according to a general method of assessing
regional groundwater resources, which starts with:
Conceptualization of the hydrogeology, which consists of building-up the
three dimensional hydrogeological setting based on surface and subsurface
geology, followed by estimation of the regional groundwater surface. After
that the conceptual groundwater model can be expanded by the identification
of flow systems, in particular intake areas and zones with groundwater
discharge.
Water budget. Once the conceptual model is completed, in the sense that all
the available information, geologic, water table and base flow data has been
considered, the usej of remote sensing for the upper boundary condition is
discussed, namely recharge, evapotranspiration loss and estimation of water
use for irrigation from groundwater.
Quite some space is devoted to the recharge for two reasons: (1) Remote sensing
offers unique possibilities in assessing the spatial patterns, and (2) Groundwater is
or is becoming a scarce resource in quantity and quality and this resource can be
influenced by the conditions near the surface, in particular by the land cover and
G. A. Schultz et al. (eds.), Remote Sensing in Hydrology and Water Management
© Springer-Verlag Berlin Heidelberg 2000