WASH Cluster – Emergency Training GWD GWD2 1 1 Groundwater Development and Drilling Session 2 Characteristics of Groundwater Systems

WASH Cluster – Emergency Training GWD GWD2 2 You can’t drill anywhere and get groundwater Groundwater is not static – it flows through pores in rocks Aquifers are not underground rivers – only really in caves Not all groundwater obtained will be drinkable Debunking Groundwater Myths 2

WASH Cluster – Emergency Training GWD GWD2 3 Interconnection and Flow 3 Interconnection of the pores in rock or soil allows water to: enter the groundwater, be stored in an aquifer below ground, flow through the subsurface, discharge naturally to a river, swamp, spring or the sea, be recovered in a well or bore This all relates to the geology of the area and the different types of soil and rock.

WASH Cluster – Emergency Training GWD GWD2 4 Groundwater Recharge 4 Recharge is the process by which water gets into an aquifer. Recharge quiz

WASH Cluster – Emergency Training GWD GWD2 5 Rainfall to Groundwater Water entering the soil is used by plants (Evapotranspiration) Water that isn’t used or stored in the soil seeps down below water table – becomes Groundwater - known as recharge Aquifer RAINFALL Some rainfall runs off across ground surface, Some evaporates at the surface Remainder enters soil Storage of water in the soil (unsaturated zone) Becoming wetter closer to water table

WASH Cluster – Emergency Training GWD GWD2 6 Groundwater flows through an aquifer under an hydraulic gradient effectively the difference in potential energy of the water –(hydrogeologists and groundwater engineers refer to the potential as the “head”). Groundwater flows from areas of higher to lower head Groundwater Flow 6

WASH Cluster – Emergency Training GWD GWD2 7 EXERCISE 1 7

WASH Cluster – Emergency Training GWD GWD2 8 EXERCISE 1 Cross section 8

WASH Cluster – Emergency Training GWD GWD2 9 Rate of groundwater flow is a function of the hydraulic gradient Flow through the soil and within aquifers occurs by different pathways through different types of rocks Rate of groundwater flow 9

WASH Cluster – Emergency Training GWD GWD2 10 Permeability 10 Rock permeability governs the ease at which groundwater flows after Bear and Verruijt, 1987

WASH Cluster – Emergency Training GWD GWD2 11 Impact on well supply 11 After: Don Armstrong, Australian Groundwater School, AMF course notes 1987 (unpublished)

WASH Cluster – Emergency Training GWD GWD2 12 Aquifers and Aquitards 12 Aquifer: A layer of soil or rock that has relatively higher porosity and permeability than the surrounding layers, enabling usable quantities of water to be extracted. Aquitard :A layer of soil or rock that has relatively lower porosity and/or permeability than the surrounding layers, limiting the movement of groundwater through it and the capacity to extract useable quantities of water.

WASH Cluster – Emergency Training GWD GWD2 13 Activity Fill the kettle Plug spout with cork Keep filling Use different things to plug spout Time how long it takes for water to come out

WASH Cluster – Emergency Training GWD GWD2 14 Confined and Unconfined aquifers 14

WASH Cluster – Emergency Training GWD GWD2 15 Water flows preferentially through higher permeability zones Water will move to areas that have least restriction to flow Groundwater will discharge at a point where constraints are released Groundwater Discharge 15 DISCHARGE QUIZ

WASH Cluster – Emergency Training GWD GWD2 16 Discharge sites 16 after Bear and Verruijt, 1987

WASH Cluster – Emergency Training GWD GWD2 17 EXERCISE 2 cross section 17 Seepage - springs or soaks

WASH Cluster – Emergency Training GWD GWD2 18 Climatic influence on Groundwater occurrence 18

WASH Cluster – Emergency Training GWD GWD2 19 Springs 19

WASH Cluster – Emergency Training GWD GWD2 20 Interaction with Rivers Water table above river Groundwater discharge to river 20

WASH Cluster – Emergency Training GWD GWD2 21 Interaction with Rivers High flow in the river can lead to seepage into the groundwater 21

WASH Cluster – Emergency Training GWD GWD2 22 River above the water table Downward seepage into groundwater 22

WASH Cluster – Emergency Training GWD GWD2 23 Coastal Zones 23

WASH Cluster – Emergency Training GWD GWD2 24 Variability of Water Quality 24 From Elrail et al 2009 Groundwater salinity can vary within the same aquifer