Surface water iswater located on top ofland, forming terrestrial (surrounding by land on all sides)waterbodies, and may also be referred to asblue water, opposed to theseawater andwaterbodies like theocean.
The vast majority of surface water is produced byprecipitation. As theclimate warms in the spring,snowmelt runs off towards nearby streams and rivers contributing towards a large portion of humandrinking water. Levels of surface water lessen as a result ofevaporation as well as water moving into the ground becomingground-water. Alongside being used for drinking water, surface water is also used for irrigation,wastewater treatment,livestock, industrial uses,hydropower, and recreation.[1] For USGS water-use reports, surface water is consideredfreshwater when it contains less than 1,000 milligrams per liter (mg/L) of dissolved solids.[2]
There are three major types of surface water.Permanent (perennial) surface waters are present year round, and includeslakes,rivers andwetlands (marshes andswamps).Semi-permanent (ephemeral) surface water refers to bodies of water that are only present at certain times of the year including seasonally drychannels such ascreeks,lagoons andwaterholes.Human-made surface water is water that can be continued byinfrastructures that humans have assembled. This would bedammedartificial lakes,canals and artificial ponds (e.g.garden ponds) or swamps.[3] The surface water held by dams can be used forrenewable energy in the form of hydropower. Hydropower is the forcing of surface water sourced from rivers and streams to produce energy.[4]
Surface water can be measured as annual runoff. This includes the amount of rain and snowmelt drainage left after the uptake of nature, evaporation from land, and transpiration from vegetation. In areas such asCalifornia, the California Water Science Center records the flow of surface water and annual runoff by utilizing a network of approximately 500 stream gages collecting real time data from all across the state. This then contributes to the 8,000 stream gage stations that are overseen by theUSGS national stream gage record. This in turn has provided to date records and documents of water data over the years. Management teams that oversee the distribution of water are then able to make decisions of adequate water supply to sectors. These include municipal, industrial, agricultural, renewable energy (hydropower), and storage in reservoirs.[5]
Due toclimate change, sea ice andglaciers are melting, contributing to the rise in sea levels. As a result, salt water from the ocean is beginning to infiltrate our freshwateraquifers contaminating water used for urban and agricultural services. It is also affecting surroundingecosystems as it places stress on the wildlife inhabiting those areas. It was recorded by the NOAA in the years 2012 to 2016,ice sheets inGreenland and theAntarctic reduced by 247 billion tons per year.[6] This number will continue to increase as global warming persists.
Climate change has a direct connection with thewater cycle. It has increased evaporation yet decreased precipitation, runoff, groundwater, and soil moisture. This has altered surface water levels. Climate change also enhances the existing challenges we face in water quality. The quality of surface water is based on the chemical inputs from the surrounding elements such as the air and the nearby landscape. When these elements are polluted due to human activity, it alters the chemistry of the water.[7]
Surface andgroundwater are two separate entities, so they must be regarded as such. However, there is an ever-increasing need for management of the two as they are part of an interrelated system that is paramount when the demand for water exceeds the available supply (Fetter 464). Depletion of surface and ground water sources for public consumption (including industrial, commercial, and residential) is caused by over-pumping.Aquifers near river systems that are over-pumped have been known to deplete surface water sources as well. Research supporting this has been found in numerous water budgets for a multitude of cities.
Response times for anaquifer are long (Young & Bredehoeft 1972). However, a total ban on ground water usage during water recessions would allow surface water to retain better levels required for sustainableaquatic life. By reducing ground water pumping, the surface water supplies will be able to maintain their levels, as they recharge from directprecipitation,surface runoff, etc.
It is recorded by theEnvironmental Protection Agency (EPA), that approximately 68 percent of water provided to communities in the United States comes from surface water.[8]
