The water on earth arrived 4-5 billion years ago, and is all the water that ever was or will be on earth. More than 97% of the Earth’s water lies within the oceans. The remaining 2.8% is the water within the land masses- lakes, rivers and groundwater. The land masses contain all the fresh water on the planet. Most of that freshwater is contained in icecaps and glaciers (for now). The remaining fresh water is stored primarily in the subsurface as ground water and a lesser amount is stored in lakes and flows as rivers which are renewed by rainfall.
For more than 4 billion years, the original water in the atmosphere has fallen back to the surface as raindrops or snow, flowed into streams and rivers and on to the oceans, then evaporated when heated by the sun and formed into clouds in the sky. The water on earth never rests, it is constantly moving within the complex pathways of the hydrologic cycle and over a wide variety of time scales. Water moves quickly through some pathways -rain falling in summer may return to the atmosphere in a matter of hours or days by evaporation. Water may travel through other pathways for years, decades, centuries, or more by being absorbed into the ground and percolating below to be trapped in bedrock as groundwater.
The water molecules in our glass of drinking water have traveled through the air, ground, streams, and oceans over and over again in the billions of years since the earth formed. The water has absorbed various particles in the journey beyond the H2O molecules themselves. In every cup of water that we drink are H2O molecules that have previously traveled the earth and through the intestines of countless generations of fish, birds and mammals, yet the water remained fresh and clean.
The processes of nature sterilizes water and prepares it for reuse. When water droplets are evaporated by exposure to ultraviolet rays of the sun, or high levels of oxygen when flowing roughly down waterfalls bacteria and viruses are degraded or destroyed and most biological contaminants are removed during the journey.When plant roots absorb nutrients and H2O molecules the water is transported to the leaves and evaporated back into the atmosphere. "Transpiration" moves H2O molecules from liquid to vapor form, and sterilizes the water in the process. Transpiration removes water from soil and streams, and releases it as water vapor in the atmosphere.
When our nation was occupied by few hunter gatherers, population levels were very low. Water contamination by their human wastes were not a major health issue because the natural processes were adequate and wildlife in natural areas would rarely be concentrated enough to create sufficient waste to affect water quality in the east. (The environmental impact of the vast herds of buffalo are for a different discussion.) As water flowed to natural streams, exposure to sunlight/oxygen soon killed most harmful bacteria and viruses excreted by wildlife. Water was abundant.
Water is precious and for too long we have taken it for granted and assumed it should be cheap. Today many once-natural areas have been developed as farms, towns, suburbs and cities. The human population has grown so large and humans are concentrated in such density that natural processes cannot clean our wastewater before the next community downstream plans to use it for drinking water. We now treat our waste water and drinking water to remove contaminants, but we create contaminants faster than we remove them. We have created chemicals to spray on our land, rinse down the drain, flush down the toilet and dump into our rivers; and our suburban communities are exacerbating "natural" wildlife pollution, by removing massive amounts of natural habitat and concentration the wildlife populations in narrow strips of land. Water pollution is a modern phenomenon created by mankind and we excel at it.
Not only are we contaminating water, but we are over using it. The earth has a fixed amount of water and only a tiny fraction is available fresh water, and availability is complicated by the variability in weather and the variable length of different parts of the water cycle. Precipitation does not fall in the same amounts throughout the world, in a country, or even a region and varies from year to year. Nonetheless two Dutch scientists in a well-known study estimated the consumptive use of water for agriculture, and estimated that over 90% of water used globally is consumed by crops and agriculture in general. Mankind’s demand for fresh water is predominately for food and we are on a trajectory towards running out of both.
Communities and regions across the United States are facing water challenges impacting millions of lives and the will cost billions of dollars to address.. Last month in conjunction with the United Nations World Water Day, the White House hosted a Water Summit to raise awareness of water issues and potential solutions in the United States. This was done in the shadow of the recent events, including record-breaking drought in the West, severe flooding in the Southeast, and the water-quality crisis in Flint, Michigan. Our water infrastrcture is falling apart, our water supplies are being contaminated, over used and falling. The White House Summit was a beginning of the process of building consensus, of catalyzing ideas and actions to help build a sustainable and secure water future through innovative science and technology.
While water availability, sustainability and quality are issues almost everywhere in our nation (and for that matter in the world), the solutions are very local. The White House Proposed solutions
are mostly tilted towards forecasting, monitoring and addressing drought. Drought is only one problem. The others are managing our water resources sustainably - ensuring that we do not use up our groundwater; and making sure that our drinking water is clean and uncontaminated. The solutions for Flint, Michigan, our own Washington Metropolitan area and Los Angelis are very different. Only the need for political will and money are the same.
The Washington Metropolitan area is fortunate to have the Interstate Commission on the Potomac River Basin, ICPRB, which was authorized by congress in 1940
to address the pollution of the river. In response to the droughts of the 1960’s and 1970’s the ICPRB facilitated the creation of the Potomac River Low Flow Allocation Agreement in 1978
. The ICPRB has been able to coordinate all the political entities, Maryland, Virginia, Fairfax Water, Washington DC, the federal government and counties and cities within the watershed to address the basin’s major challenges, including water quality impairments, water supply and restrictions, flooding, nonpoint source pollution and emerging contaminates. There is one area that has been overlooked- groundwater. The sustainability and protection of groundwater has not been addressed.
Sustainable groundwater use in Virginia is not tracked or managed by DEQ or any other agency for that matter. Groundwater is not unlimited. Our groundwater is at risk. We are fortunate in the water rich climate of our region that the groundwater is being recharged, though the Atlantic Coastal Plain aquifer is under stress and is being used up faster than its recharge rate. This has been confirmed by measurements of groundwater levels, modeling of the aquifer system by the U.S. Geological Survey (USGS) and measurements of changes in gravity by the GRACE satellite project at NASA over the past 12 years of data collecting
Less is known about the sustainability of the smaller groundwater basins in the region. Our own Culpeper Basin that feeds the private wells in the Rural Crescent of Prince William and areas of Loudoun and Fauquier counties is an example. Use of the aquifer has not been examined. We do not evaluate a development’s impact on groundwater from changes in ground cover by roads and buildings nor look to proposed water withdrawals to determine if a proposed additional use of groundwater is sustainable before it is granted. Our groundwater resources like the waters of the Potomac are not unlimited, and cannot be ignored. The White House has turned toward sustainable water and because water is a local issue we need to turn towards sustainability also.