Perserve the Watershed

Data centers directly and indirectly use water; however, they also have significant impacts on watersheds and the hydrologic cycle. In Virginia, data centers have be built on Greenfields and end up replacing natural open space with 7-8 football fields of building surrounded by cleared, compacted and paved land.  One data center or even a few dozen are fine, but that's not what we are doing. Reportedly, we currently have 51 million square feet of data centers in Northern Virginia and we as a region are running headlong to more than quadruple that number. Beyond the power use, that will be the biggest impact of Data Center Alley's expansion into Montgomery county and south beyond Manassas, VA. they will directly use enough water as the existing population and reduce our water availability and quality at the same time. 

The impervious cover, compacted soils, pavement and loss of natural open spaces from these giant hyperscale data centers will increase , flooding and  runoff to creeks and rivers. The larger volume, velocity and duration of stormwater flows will act like sandpaper on stream banks, intensifying the erosion and sediment transport from the landscape and stream banks. This often causes channel erosion, clogged stream channels, and habitat damage and road flooding.

Land use changes that significantly increase impervious cover from roads, pavement and buildings does two things. It reduces the open area for rain and snow to seep into the ground and percolate into the groundwater and  the impervious surfaces cause stormwater velocity to increase preventing water from having enough time to percolate into the earth, increasing storm flooding and preventing recharge of groundwater from occurring. 

 Increased stormwater volumes, sediment loads and pollutant loads are a direct result of clearing the land of trees and vegetation, construction activities for buildings and roads. Slowly, this can reduce groundwater supply over time. Groundwater serves as the savings account for streams,  rivers and lakes. Increasing population density, increases in industrial water use and reducing recharge as we’ve been doing slowly reduces groundwater levels over time as the groundwater is used up. Groundwater changes are not abrupt and problems with water supply tend to happen very  slowly and are missed until it is critical and a drought unveils it. 

With natural open groundcover, 25% of rain infiltrates into the aquifer and only 10% ends up as runoff. As imperviousness increases, less water infiltrates and more and more runs off. In highly urbanized areas, over one-half of all rain becomes surface runoff a five fold increase, and deep infiltration is only a fraction of what it was naturally occurring.

In a series of studies from the 20^th century in California found this pattern of degradation. The well known example is of Los Penasquitos Creek in San Diego County, watershed development grew from 9% to 37% urbanization between 1966-2000. From 1973-2000, the total annual urban runoff in the upper watershed increased by 4% per year, resulting in more than a 100% increase in runoff for the measured time period. The flood magnitude for the 1-2 year storm also increased by more than 5 times from 1965-2000.

When the impervious cover in a watershed exceeds 5%-20% the impacts are:

• Excessive stream channel erosion from  both the streambed and stream banks.
• Reduced groundwater recharge
• Increased size and frequency of 1-2 year floods
• Decreased movement of groundwater to surface water, perennial streams will become ephemeral 
• Loss of streambank tree cover
• Increased contaminants in water 

When generally wooded and open rural areas are cleared, graded and compacted and developed for data centers, we begin the destruction of parts of our watershed.  This must be limited to preserve our source of drinking water. We have no replacement. Otherwise, the development will increase stormwater runoff i in quantity and velocity washing away stream banks, flooding roads and buildings carrying fertilizers, oil and grease, and road salt to the streams and rivers and our reservoirs.

The consequences of this change are a decrease in the volume of water that percolates into the ground, and a resulting increase in volume of stormwater and decrease in quality of surface water. These hydrological changes have significant implications for the quantity of fresh, clean water that is available for use by humans, fish and wildlife. If taken to a high enough extent of development, to survive in the region we will need to build more reservioirs and increase the water treatment lines to drink essentially storm flood waters.

Data centers are part of our modern world. What we need to do is manage our watershed to minimize the damage to our essential water resources. Let’s talk about what we need to do to manage the impacts from data centers. Data center companies are more than cautious about sharing any information they don’t have to. Many are not even collecting data at all.

We cannot plan for the future of Virginia without planning and managing our water resources.  Climate is changing, data centers are adding extra pressure in their direct water use to regions already challenged with meeting public, agricultural, and industrial needs. We have not had a drought of any significance in in more than 15 years. What will we find when the drought comes? We need to make sure our region will have a sustainable source of quality drinking water. To do this, data is essential. We need to know and track how much water data centers use and what is happening to our water resources and land cover. Here are some simple suggestions for just understanding what we are doing. 

• All groundwater wells (other than domestic individual supply) need to be permitted with monthly volume limits and required reporting.
• An adequate number of groundwater monitoring wells need to be added to the open access USGS network.   
• To fight inland salinization, data centers need to remove the salt from blow down and waste water and control the use of road salt on their sites.
• Above ground fuel storage tanks will have adequate secondary containment to prevent release of fuel to the environment.
• Generators need to be permitted as a single source.
• Mature trees need to be preserved. Natural open space (Woodland buffers) need to be increased in size to 500 foot to avoid the edge effect and so that they can provide environmental services including stormwater management and groundwater recharge. 
• Virginia needs to manage the amount of impervious surfaces in watersheds keeping it between 5-10% and avoiding fragmented open space.