Although it represents a third of the planet, water - the universal solvent - is a scarce source and must be treated to make it available for human consumption. Water is molecularly structured to be able to dissolve a variety of different substances, so it is considered a good solvent. It is a bent molecule because it has a polar arrangement of oxygen (negative charge) and hydrogen (positive charge) atoms. Water is easily attracted to other molecules, sometimes to the point of disrupting the forces of attraction and causing it to dissolve (Perlman, 2014). Water quality is based on both chemical and aesthetic factors. To determine water quality, temperature, pH, TDS - Total Dissolved Solids, dissolved oxygen and turbidity of the water will be tested. Temperature affects chemical elements, mainly dissolved oxygen levels in surface waters and biological properties such as photosynthesis of aquatic plants, etc. Hot water is less able to hold dissolved oxygen and the solubility of oxygen decreases. As the temperature increases, an exothermic reaction occurs, resulting in the release of heat in the form of gas molecules. Kinetic energy increases the movement of gas molecules, breaking intermolecular bonds and separating them from water molecules. As a result, the amount of solute available to dissolve in water is less. Thermal pollution is another major problem caused when water sources (like streams) are hotter than the body of water they join. This can come from urban runoff such as heated water on roads, industrial discharges - hot water used to cool equipment and canopy removal which reduces shade, increases erosion and leads to more large amount of sediment in the water (Unknown, nd). This can lead to increased TDS in the water. TDS measures the medium of the paper......SDW, nd TDS and pH. [Online] Available at: www.safewater.org/PDFS/resourcesknowthefacts/TDS_AND%20_pH.pdf [Accessed May 11, 2104]. Frey, RC a. R., 1998. Water hardness – Experiment on inorganic reactions. [Online]Available at: www.chemistry.wustl.edu/-edudev/LabTutorials/WaterFreshWater/hardness.html[Accessed May 5, 2014].Johnson, R., Holman, S. & Holmquist, D., 1999. Water Quality Test Summary. [Online]Available at: www.sasta.asn.au/v2/adc/datalogging/DataSinglePagePDFs/ADCBookDatalog13-23.pdf[Accessed 15 May 2014].Perlman, H., 2014. The USGS Water Science School. [Online]Available at: http://water.usgs.gov/edu/qa-solvent.html[Accessed May 5, 2014].Unknown, and RAMP, Regional Aquatics Monitoring Program. [Online]Available at: www.ramp-alberta.org/river/water+sediment+quality/chemical/temperature+nd+dissolved+oxygen.aspx[Accessed May 10 2014].