Changes in hydrological cycle have been experienced as the result of the global climate change which may have caused undetermined increase or decrease in the location and reserve of water resources which are already undetermined in various parts of the world. These events have put the concept of “Reliable Flow” into agenda. Among today’s subject matters related to water, water quality in addition to its amount is an important issue. Altered land use and land management practices (e.g. the use of agrochemicals) have changed hydrological cycle. As a consequence, amount and quality of water reserves are consistently worsening.