Water engineering notes for civil engineering students

Water engineering notes for civil engineering students

5. Components of Well system
This Water Well Diagram Illustrates the Components Found in Proper Well
Construction

6. Here are some of the more important elements included in the water well diagram
above.
Borehole – The borehole should be about 50mm (2 inches) wider all around than the well
casing. The borehole needs to be clear of obstructions all the way down, and should be deep
enough to reach the lowest expected water level.
Casing – The well casing lines the borehole and is often made of PVC pipe. As stated above,
if the borehole is 200mm (8 inches) then the well casing would be 100mm (4 inches)
making a space of 50mm (2 inches) all around the casing. The bottom of the well casing is
capped and the lower section is slotted to permit water to pass into the casing.
Gravel Pack – This layer of coarse sand or gravel fills the 50mm (2 inch) space between
the well casing and the borehole. The gravel pack allows water to flow from the aquifer into
the well and should extend about 1 meter above the well screen.

7. Pump Pad – Along with the sanitary seal, the pump pad surface water from contaminating
the well. The pump pad is made of concrete and should be thick enough and reinforced with
re-bar to keep it from cracking. Cracking would allow surface water to seep into the well.
Sanitary Seal – The sanitary seal is made of a slurry of bentonite clay and cement.
The pump pad and sanitary seal are extremely important in preventing well contamination.
Selection of sites for construction of Water Wells
Finding the right spot for a water well ensures a dependable water supply, protects against
contamination, and reduces long-term costs. Here’s a quick overview of the steps:
• Check Water Availability: Study groundwater levels and geological formations like sand or
fractured rock for easier access.
• Read Geology Reports: Use resources like USGS maps or state surveys to identify water-
bearing zones.
• Check Local Rules: Follow setback distances and zoning laws to avoid fines or
contamination risks.
• Find Safety Hazards: Assess nearby risks like septic tanks, flood zones, or agricultural
runoff.
• Plan for Access: Ensure proper roads and clearance for drilling and maintenance equipment.
• Work with Experts: Hire hydrogeologists and licensed contractors for detailed site
assessments.
• Use Modern Tools: Leverage digital mapping, underground imaging, and flow analysis for
precise well placement.
Methods used for well site selection:
1. Geological Methods
• Study of surface rocks, soil types, and landforms.
• Identifies aquifer-bearing formations (e.g., sand, gravel, fractured rocks).
• Uses geological maps, outcrops, and soil profiles to locate groundwater potential zones.
2. Geophysical Methods
• Use instruments to investigate underground water without digging.
• Common techniques:
o Electrical Resistivity – detects changes in subsurface resistance (water lowers
resistivity).
o Seismic Refraction – determines depth to bedrock and aquifers.
• Helps estimate aquifer depth, thickness, and yield.
3. Hydrogeological Methods

8. • Involves studying groundwater occurrence, movement, and recharge.
• Uses test boreholes, pumping tests, and water balance studies.
• Assesses aquifer properties (permeability, transmissivity, storativity).
4. Remote Sensing & GIS
• Uses satellite imagery, aerial photos, and GIS mapping.
• Identifies vegetation patterns, drainage, lineaments (faults/fractures).
• Useful for regional groundwater exploration.
5. Traditional/Empirical Methods
• Based on local knowledge and observation of indicators:
o Presence of water-loving plants (e.g., reeds, palms).
o Damp soils, termite mounds, animal tracks.
• Cheaper but less reliable compared to scientific methods.