1. Dams and Water Supply The specification states that in relation to dams you need to be able to: Interpret the geological factors affecting the construction and siting of dams and reservoirs.

2. Dams Nature of the underlying rocks. Depth of weathered rock: – because weathered rock is not as strong as unweathered rock. Mechanical strength of the rock/load bearing capacity: –To support the massive weight of the dam wall. Impermeable rocks are important, why? –To stop the water infiltrating away.

3. Dams 2 Suitable seal between rock and dam. Seal could be improved by grouting. Use of a cut off curtain to stop water leakage. Lack of faults – to stop leaks. Lack of jointing – to stop leaks.

4. Dams 3 Strata dip upstream - reduces the possibility of instability of the structure. Lack of folds which could permit leakage due to joints at the hinge.

5. Dams 4 Lack of seismic activity which could crack the dam or cause landslips. Lack of landslips. Lack of volcanic activity. Absence of underground workings or presence of hidden river channels which could lead to the possibility of collapse.

6. Dams 5 Suitable building materials such as hard rock/concrete for concrete/masonry dams. Clay/sediments for earth dam/aggregates.

7. Dams 6 Other obvious features include: A steep sided valley to capture the water. A catchment area that has a reasonable amount of rainfall. A catchment area with some impermeable rocks to allow runoff to the river. Lack of sediments in feeder streams which could lead to the silting up of the reservoir.

8. Water Supply The specification states that you need to be able to: Describe water supply in relation to river, reservoir and underground sources. Understand the advantages and disadvantages of surface and underground supply. Understand that water resources are both renewable and sustainable if carefully developed.

9. Water Supply: Sources The 3 main sources are: Rivers Reservoirs Underground or groundwater. We have already discussed different types of groundwater aquifers and reservoirs/dams. I think you already know about rivers too. Therefore we will move onto the next section:

10. Surface v Underground Supplies Surface good points: Easily accessible. Can be used for recreation or navigation. Can be of scenic beauty.

11. Surface v Underground Supplies Surface bad points: May be polluted by effluent or contaminated runoff. During droughts water may be lost. In hot areas evaporation may remove a large proportion of the water. Of no use in arid regions (central Australia).

12. Surface v Underground Supplies Underground Good Points. Spring water becomes pure and drinkable by being filtered by passage through sediments. Reliable/constant - non seasonal supply. Accessible even in areas with no rain. Maintained hydrostatic pressure. Lack of surface pollutants

13. Surface v Underground Supplies Underground negative points: problem of leachate and pollution from waste tips. problem of recharge and over pumping. spring water becomes unpalatable if: –leachates contaminate the flow –seawater contaminates the flow

14. Surface v Underground Supplies too many salts in artesian supply makes water saline. nitrates/fertiliser contaminate the water. radioactive water from nuclear waste. the water table may fall during summer months cutting supply. the water table may be lowered by over pumping. recharge may be slow. hydrostatic pressure falls through time.

15. Sustainable Water Supply The specification states that you need to: Understand that water resources are both renewable and sustainable if carefully developed. Water moves through the water cycle and is just borrowed by humans. As long as it is put back into the system in a reasonably uncontaminated way then it can be renewable and it’s use sustained. Overuse for irrigation in hot climates can make the water saline which can be a problem.