Computer-enhanced Landsat images for ground water exploration in the northern Arabian Shield : Ha'il test site

Discovery of new ground water reserves is very important to the resettlement of the nomadic people and the agricultural development in arid lands.

Two Landsat Multispectral Scanner (MSS) and one Return Beam Vidicon (RBV) digital images depicting the Ha'il Region of Saudi Arabia were subjected to computer corrections and enhancement techniques to highlight geological, soil, and land cover information applicable to discovery of new ground water reserves.

Correction techniques were used to remove the undesired effects of sun-elevation variance, atmospheric haze, striping noise patterns, dropped lines, and geometric distortions; thereby rendering "clean" data bases for all bands.

Various enhancement techniques were then applied to the data bases individually to produce different enhanced images. The enhancement techniques were linear and sinusoidal stretches, high—pass filter, horizontal, vertical, and diagonal derivatives, ratioing, and simulated natural color. Various processing methods, such as merging of the digital MSS to RBV data, temporal analysis of different dates, and normalized ratio were obtained to distinguish the surface features. Also, various false-color composites were generated to detect the Hail Region surface features and were then assessed and ranked in terms of their ability to depict the phenomena of interest.

These computer-enhanced MSS and RBV images were used for developing a geohydrologic model. The geohydrologic model for ground water exploration was developed by image interpretation which has been utilized to map the following surface features:

1. Distribution of exposed bedrock.

2. Distribution and direction of major wadis.

3. Distribution of vegetation.

4. Location of lineaments in bedrock.

5. Location of playas.

6. Location of dikes.

These surface features were used as important clues for locating ground water reserves in the area and for selection of sites where potential for ground water discovery exists.

The geohydrologic model was successful in selecting and locating new ground water reserves at a number of sites in the Ha'il Region.