LOWING WATER FOR GREENER NEIGHBORHOODS S

By Dr. Rob Moir, Ph.D.

Climate Change has brought fiercer storms with devastating floods and long-lasting droughts that stressed and killed plants and animals. Once we controlled water. These days, water is in control and is harming us.

What if we changed our relationship with water to understand its behavior better? What if we were more respectful and asked, what does water want? Communities that have taken a less confrontational and more collaborative approach with water have created better places where people are happier.

Louisville, Kentucky, suffered a great deluge when 7.2 inches of rain fell in just 78 minutes.

Flood waters that cataracted through proper- ties at the University of Louisville caused $21 million in damages.

The university responded and adapted with various "green infrastructure" projects deployed to help keep stormwater runoff out of the combined sewer system.

The university slowed water by absorbing changes to the campus landscape. They disconnected downspouts, put out rain barrels, built cisterns, installed vegetated roofs, and built rain gardens and bioswales to facilitate groundwater recharge through infiltration. Pervious pavement and permeable pavers replaced impervious surfaces in lots, roadways, plazas, and sidewalks. Large underground infiltration basins were installed for remaining hard surfaces and fast runoff areas.

The University of Louisville gained a better understanding of sustainable water management. The university is now diverting about 72 million gallons of stormwater yearly, has a greener campus, and should never again suffer damages during rainstorms.

Farmers in Watsonville, California, irrigate strawberries, artichokes, cauliflower, broccoli, lettuce, raspberries, and natural plants with water pumped up from the aquifer beneath their fields. The trouble was the lens of water in the ground was shrinking, and saltwater from Monterey Bay was intruding.

In response to the over-pumping problem, California created the Pajaro Valley Water Management Agency (PVWMA) to charge water users for the groundwater they drew in hopes that they would use less water. Still, the groundwater diminished.

With a better understanding of water, PVWMA paid farmers to run their irrigation pumps backward to recharge groundwater with rainwater that would otherwise go into storm drains to the sea. Farmers are credited 50 percent of the recharge against their future groundwater pumping costs. That figure is conservative because some infiltrated water will flow outwards into the more comprehensive hydrologic system before the farmer can pump it out.

Paying farmers to pump stormwater into the aquifer has multiple spinoff benefits. This water helps to push seawater back into the ocean, reducing saltwater intrusion. Pumped stormwater keeps the soil moist, reducing the need to irrigate and maintaining higher groundwater levels. Best of all, there are no arguments as to who owns the water. In the Pajaro Valley, the water belongs to everyone.

In Falmouth, Massachusetts, rainwater washed fertilizer off the lawns into Little Pond. This nutrient pollution during the summer caused a harmful algal bloom that killed 16 striped basses. Falmouth adapted to increased rainfall by banning the use of fertilizers on established lawns. Ten years later, there has not been another harmful algal bloom, no fish kills, and the lawns are no less green than in towns where fertilizer is spread liberally.

Falmouth discovered that grassroots go deep into the soil without fertilizer to open it up and make it more porous and habitable for soil organisms. Long fungal strands fuse with roots to form mycorrhizal networks larger than the lawn. A single fungal strand inside the plant touches each cell. If a plant cell is stressed, perhaps by someone walking on the grass or a pest munching, it signals to the mycorrhizal network what it needs to grow and remedy the situation. Bacteria respond to signals to put what is requested into the "wood wide web" that is transported to the grass.

Plants combine water and carbon dioxide and create carbohydrates with energy from the sun. Absent sunlight in the soil, root exudate is a primary energy source for soil organisms. With grasses, about half of the liquid carbon grows the plant, and half is pushed out of root tips to build soil.

Lawn soils are the best because they are high in organic carbon, mostly root exudate plus detritus. When the carbon-mineral mixture goes through a chemical transformation, it becomes humus. Humus is black in rich soil, high in nutrients, where water and oxygen move easily, thanks partly to the capillary action of roots and worms. This soil swells greatly when it rains. Four inches of lawn soil can hold seven inches of rainwater. The ability to absorb and hold water is greatly reduced in other soils. Sandy soils that are three inches deep will hold up to three inches of rainwater.

In Springfield, Massachusetts, 16 lawns were not fertilized or watered. Lawns were mowed with the blade set to 3.5 to 4 inches high, and cuttings were left on the lawn. A third of the lawns were cut every week. A third cut every two weeks and a third every three weeks. These lawns were found to have 36 kinds of flowers. The lawns cut every two weeks had the greatest diversity of bee species. Overall, 111 bee species! The one-week-cut lawns needed to give the flowers enough time, and perhaps the three-week cut had higher grasses than some bees prefer.1

Water was a determining factor for bee diversity. The bees of natural lawns are smaller than hiving bees and are more sensitive to falling water drops. Some are pith-nesting bees that cannot survive "a good soak." Researchers have also found that bee diversity goes down with inclement weather.

The four communities, one suffering from flood damages, one losing groundwater to agriculture, one blaming lawns for harmful algal blooms, and one keeping lawns while increasing wildflower and bee abundance with greater biodiversity, experienced a dramatic shift from a scarcity mind- set to one of shared abundance. Arguments and the setting of priorities, and tradeoffs gave way to collaborative efforts, helping one another with quality-of-life benefits for everyone, even including what's good for nature.

Our rivers are fed with cool water that seeps in from the ground or gurgles from springs. Rivers depend on water in aquifers. Diminishing water in the ground is the reason for low water flows. There has been a great loss of aquifer recharge to lands covered by impervious surfaces. The faster water flows across the surface; the less will infiltrate into the ground. Topping off the aridification of neighborhoods is the loss of soil.2

Sometimes overlooked in all the climate change talk has been the importance of soil to the world's water and carbon cycles. Soils covering less than 10 percent of the Earth are more than three times the amount of carbon found in the air. Carbon dioxide amounts to 800 billion tons of carbon worldwide versus 2,500 billion tons of organic carbon in soils. Total global biomass is 600 billion tons carbon.

Here's the problem. The more carbon and water we have in the air, the less carbon and water we have in the soil. The less water and carbon in the soil, the fewer plants can grow, and the more carbon and water are left in the atmosphere. It's a vicious circle that we can change. The nature-based solution is to get more organic carbon into the soil, and water will follow.

In the best of conditions, a natural lawn can build an inch of soil in a year. No other plant comes close to the high percentage of manufactured carbon pushed out as root exudates. For a lawn that is 240 square feet, an inch of soil weighs one ton.

For one ton of root exudate, grass plants must make about two tons of carbohydrates, with half going to biomass and half coming out of the roots to build soil. Carbohydrate molecular weight is 3.64 times that of carbon dioxide. For a ton of soil, 7.28 tons of carbon is pulled out of the atmosphere.

If Massachusetts were to pay property owners by the ton for storing carbon as soil, there would be incentives to stop using chemicals, including quick-release fertilizers, and to replace hard surfaces with grass. With deeper soils, the need for watering is less, and plants stay green longer.

There's more. If Massachusetts incentivized property owners to pump stormwater into the ground, there would be reductions in stormwater damages, more water in the land, including soils, and steadier water flows in rivers during dry months.

Pumping is required when we simply do not have sufficient permeable surface areas needed for infiltration. The State paying property owners to pump water avoids the high one-time costs of purchasing real estate. Paying to pump is more than just in the application. Fixing a value on water would enable banks to make revenue projections and finance the construction of their neighborhood Community Water and Energy Resource Centers.

If an institution in Cambridge, Massachusetts, put 72 million gallons of water into the ground, as the University of Louisville does annually, essentially running the water meter backward at current water rates, it would save the institution hundreds of thousands of dollars.

Unlike generating energy, the cost of managing water does not go down when put back into the ground. Governments must provide upfront funding for municipal waterworks to cover lost revenue. However, this expense should be more than offset by the savings in stormwater and drought damages.

We can adapt to climate change and reduce deluges or droughts by slowing water down with soil, with more green spaces, replacing or on top of concrete, and actively putting water back into the ground. Research indicates we can slow sea level rise by as much as 25%.

Working with climate change, we may set up a rainy-day fund measured in gallons of water. During extreme rainfalls, property owners could pump water into the ground and be compensated with reduced water bills. Property owners are also compensated for storing carbon by the ton of new soil.

By investing in pumping water and building soil in the ground, the Commonwealth would see big returns with more resilience during droughts, less need to water plants, fewer flood damages, more water in our cold stream rivers during dry periods, and a reduction in sea level rise. More difficult to quantify, but no less important, are the quality-of-life improvements when there is more green vegetation with shade and windbreaks, more cooling in summer (evaporation), and more warming when it's cold (condensation). Finally, there will be more verdant nature in our local landscapes and happier people in our neighborhoods.

1 https://academic.oup.com/aesa/article/109/5/713/2195339

2. https://e360.yale.edu/features/soil_as_carbon_ storehouse_new_weapon_in_climate_fight

Rob Moir, Ph.D., is the Executive Director of the Ocean River Institute and Director of Global Warming Solutions IE-PAC in Cambridge, Massachusetts.

He is an educator, scientist, and advocate with a proven history of institutional management and climate policy success.