What do these photos have in common? Explain how they link to the unit

Sources of Water

Rivers Reservoirs/Lakes Sources of Water Aquifers Seawater Why used historically Residence times Poor water quality  urbanisation Factors affecting suitability as a source of water Times of surplus / deficit Artificial construction Benefits to flow regime Factors considered when siting a reservoir Environmental Impacts (Effects) Case study of water demand (Devon / Cornwall) Tidal Barrages Sources of Water Porosity & Permeability Rock types (lithology) Suitable geological structures Consequences of over abstraction e.g. Subsidence, surface hydrology, ecology, saltwater incursion Desalination Cost? Aquifers Seawater

All in your notes: 1. Explain the qualities of a useful water supply 2. Explain how a useful supply controls the quality of life within a country ………….. and give one example of a region where it is holding back development

Factors considered when siting a reservoir Topography Geology Catchment Area Water Supply Existing land-use Pollution Risk Sedimentation Infra-structure

Environmental Impacts Habitat Change b. Changes in River Flow Regime c. Sedimentation d. Micro-climate

Water Demand: Case Study  Devon and Cornwall Demand is > due to pop size and affluence In summer Tourist No’s and evapotranspiration trans rate both > Shortage of stores: Aquifers limited as most bedrock is crystalline granites and therefore impermeable. Abstraction in large volumes from rivers limited as large rivers don’t exist Seasonal demand is therefore met by surface stores from reservoirs that are in upland areas often in National Parks or areas of ONB. Thus best sites are a compromise of best physical store available on the one hand whilst avoiding unacceptable environmental impact on the other.

Rivers There are a limited number of large rivers in Devon and Cornwall reducing potential abstraction sites

Geology The geology in Devon and Cornwall is mainly impermeable granite, reducing aquifer potential!

Tourism Devon and Cornwall is a tourist honeypot – therefore numbers grow in the summer > demand

National Parks and Areas of Outstanding Natural Beauty (AONB) Much of the area is NP e.g. Exmoor and Dartmoor or AONB Therefore compromise exists between reservoir sites that offer best potential storage VS minimal environmental damage!

e.g. Flooding of the Tryweryn Valley near Bala Other conflicts of interest when finding reservoir sites to provide sources of water to populations e.g. Flooding of the Tryweryn Valley near Bala Village of Capel Celyn flooded 70 people lost homes Resentment prevailed Welsh Nationalist support > “ Remember Tryweryn” Lyn Celyn: Now fills the valley and provides water for Liverpool

Another good link of this Case Study on youtube can be found here Watch it in your own time!

But what made the Tryweryn Valley such a good site for a reservoir? Access – not too remote (near to L’pool as mid-Wales.) For construction and transporting water after complete Geology – Mainly impermeable mudstones, siltstones and grits Prevents water loss. Topography – Valley widens behind dam site to increase storage Steep and deep valley: U-Shaped Geology – Glaciation has caused Steep and deep valley therefore increasing reservoir volume Land Value –Low land value mainly upland hill farms Catchment –High precipitation rate – as upland Wales has high rainfall therefore plentiful recharge Geology – Rocks folded into a syncline structure - Prevents water loss. Topography – Contours close together – Steep sided valley and deep (look at heights!) – reduces surface area for evaporation Narrow Dam Site - (800m) on flat U-shaped valley floor = stable flat foundations

So what is the Land-use like now after the Dam was built and the lake (Llyn) Celyn flooded the Valley? I can spot at least 6!