Water

A deadly chemical! Dihydrogen monoxide http://www.dhmo.org/facts.html

Water! H2O. Without water life on Earth would not exist. Three things are required for life: Carbon Energy Water

What’s so special? Odourless Colourless Maintains temperature well Not vey reactive universal solvent – nearly all molecules can dissolve in it and mix into it Lubricant

Water facts 70% of earth is covered by water 97.5% of that is in the oceans. 2.5% of it is fresh water. Only 0.01% of the fresh water can be used for drinking. Why? Humans are 70% water and we can survive for only a few days without it.

No water is ever made here. No water was ever made here. All the water you see, drink, swim in and feel has been here for billions of years. The water you drink at morning tea could have been a part of a dinosaurs urine millions of years ago – maybe even in the faeces of a celebrity you look up to….

All recycled This means that all water is constantly recycled. What is this process called? The Water Cycle

The Water Cycle

Ground water Water is held underground in pores and fractures of the rocks. If the quantity is large enough to be used it is typically called an aquifer. Water soaks into pervious rocks – rocks with pores. Sediments with billions of tiny spaces/plentiful fractures to be filled by migrating rainwater Bedrock stops continuous downward movement of water Impervious rock stops if from escaping.

Water table Simple definition: The highest underground level at which the rocks and soil in a particular area area completely wet with water

Recharge and Discharge Recharge: process by which groundwater is replenished e.g. rainwater to aquifer Volume of water infiltrating depends on: Vegetation cover Slope, soil composition Depth to water table Presence/absence of confining beds

Recharge and Discharge Discharge areas are where water leaves aquifers and flows to the surface e.g. water table intersects land surface Springs or seeps form – flow to fresh or salt water Groundwater usually flows from high to low areas due to gravity, therefore high areas recharge, low areas discharge

Questions Name two areas where water is recharged Name one area where water is discharged Why are river valleys important recharge areas? Describe how an oasis can be formed Describe the conditions for ideal recharge of water

Porosity and Permeability Important factors that dictate how much water and how easily groundwater can be held and move through it Porosity: spaces/pores between particles and their ability to absorb water depending on size and alignment. Corse grained rocks e.g. gravels, sands, sandstones etc have greater porosity Sediments rounded and equal sized – allows grouping together so larger pores for water movement

Porosity and Permeability Permeability: how well pore spaces allow fluid to flow through the material Pores must be large enough to allow interconnectivity to be permeable – very important! E.g. clays are highly porous but pore size is too small to allow them to be permeable because grains are interlocking

Questions Describe and explain why the following rocks are not both porous and permeable at the same time Clays Basalts and granites Limestones

Aquifers Aquifers are bodies of rock or layers of unconsolidated sediments capable of both storing and allowing flow of water below the surface Aquifers are both porous and permeable Confined aquifer – occur where water-bearing rocks or sediments are sandwiched between impermeable layers such as sandstone interbedded between impermeable clay layers Unconfined aquifer – found when upper surfaces coincide with the water table

Question Explain the main differences between a confined and unconfined aquifer and give an example of each. Use pages 191-12 to help you write a full answer to this question.