Mapping Surface Geology and Aquifer

The understanding of surface geology is important from defining water harvesting strategy point of view whereby one can identify recharge area, water storage area, soil moisture conservation area and any other strategies required to improve water quality and quantity in the area.

First of all, we need to have some understanding of area level strategies for land and water management in simplified ways in the form of a matrix, for example shown below water harvesting strategies based on geo-hydrological characteristics of sedimentary saline terrain.

After developing a broad understanding of the area level land and water management strategies, the Jaldoots (JDs) learn to prepare geological map of the area in the following way:

• JDs start with an explanation on geological evaluation history and origin of the area/region where the trainees come from.
• JDs are asked to divide themselves into groups and they go to different areas of village and search various stones as per their knowledge and ability to identify differently.
• JDs describe samples collected in terms of the following parameters
  • Colour
  • Hardness
  • Texture Composition
  • Size of particles
  • Any other special characteristic that JDs are able to identify
• JDs receive lecture input on different type of rock formations emphasising the following aspects:
  • Rock forming processes
  • Rock type and relevant characteristics of different types of rock
  • Igneous, Sedimentary, and Metamorphic
  • Classification of various rocks
  • Rocks occurring in the trainee's areas
• JDs also develop an understanding of hydraulic properties of rocks considering the following
  • Properties o Porosity, permeability, grain size, grain shape, water storage ability, water release ability
  • Relationship between rock and water

Once this identification is completed, JDs go for field visit to see geological conditions of the region, associated issues, challenges and opportunities for village level water resource management. The visit may help in observing effectiveness of water body locations, geological rock formations of different ages, traditional methods of water resource management and other aspects.

During field work the trainer can explain different geological and tectonic aspects of the region by showing a particular structure on site and its influence on water management. Such site may be a dyke, folded strata, fracture or fault scarp. During this explanation the trainer must ask how to identify and characterise a particular feature with the proper scientific method and what are the observations needed for this.

It is important that each JD collect samples of different rocks types and ages. After completion of the field visit, all JDs are divided into different groups to understand geology of the area as follows:

Group A - arrange all the samples from oldest to youngest age and also write the scientific and local name of each rock.

Group B - write characteristics of each sample from a rock and water relation point of view and classify it as aquifer, aquiclude, aquifuge and aquitard.

Group C - write and describe changes taking place in rocks due to associated physical processes.

Group D - write about history and geological characteristics of the rocks. Through above exercise, JDs will develop the understanding of regional geo-hydrological characteristics of the village they are studying.

After geo-hydrological understanding, JDs develop geological map the following activities:

• Meet with village elders to gain local knowledge of the hydrogeology.
• List rock formations found in village in different direction.
• Locate each formation on the basemap.
• Visit the study area and finalise the basemap with geological formation.

Finally, prepare the geological map by giving proper colour and symbols to different rock formations and geological structures like dyke and fault scarp. JDs can also show subsurface geological strata as a lithology of wells based on well inventory data in different directions of village so that one can also get the subsurface geological idea. The final outcome of this map is to show recharge areas of an aquifer.

Source : Jaldoot Resource Book