“The global water crisis – caused by drought, flood, and climate change – is less about supply than it is about recognizing water’s true value, using it efficiently, and planning for a different future.”
As the earth’s atmosphere, land and oceans warm we are seeing dramatic shifts in weather; heavier precipitation and flooding along with heat waves and drought. Water is a bit like the tale of Goldilocks. One size is too big. One size is too small. One size is just right. The water cycle not only brings rain it also cools the planet’s surface. A drizzle that lasts all day may bring several inches of rain in total but spread out across the day will soak into the ground replenishing soil moisture and groundwater. A ‘deluge’ or heavy rain event will bring many inches per hour, over-fills drains and results in catastrophic flooding. Water that moves rapidly off the landscape does not soak into the ground. It will not replenish soil water or recharge aquifers. Instead much of it ends up in the ocean.
You may think “So what, isn’t that part of the water cycle?” Ocean water evaporates, wind carries the clouds over land and it rains. It may seem as though we will never run out of water because our planet is covered with water. Unfortunately most of the water on earth (97.5%) is saline. Only a small fraction (2.5%) is fresh water that supports terrestrial life. And most of the terrestrial water is frozen in glaciers, snow pack, and ice sheets (increasingly at risk due to higher global temperatures).
All fresh water is ultimately from rain or snow but it collects in different forms. Humans obtain fresh water from melting glaciers and mountain snow (68.7%) that fill rivers, from ground water (30.1%) and from surface water such as lakes and reservoirs (< 1.2%). When global warming melts the ice and there is less snow fall in winter this source of fresh water will also be gone leaving many areas uninhabitable. Droughts caused by climate change are evaporating lakes and reservoirs. Farmers pumping water to irrigate crops are depleting aquifers. We are witnessing a water crisis that is impacting people across the world leaving tens of millions of people today at risk of running out of water. Aquifers that currently hold water hundreds even thousands of years old are being depleted and once emptied they will not refill to the same extent. All sources of fresh water are in danger of depletion.
We often take for granted how much access to water and sanitation affects the quality of our life. In many parts of the undeveloped world women and girls are still responsible for hauling water, often walking many miles carrying large cans. “Collecting water takes time. Simply to get water for drinking, bathing, cooking and other household needs, millions of women and girls spend hours every day traveling to water sources, waiting in line and carrying heavy loads – often several times a day.” Many people live without running water or basic sanitation. Even in developed countries the cost of infrastructure repairs and water treatment plants are rising forcing cities to increase the cost of these services. Access is shut off to those who cannot afford the rising price of municipal water. Life is much harder when you lose access to running water and sanitation. (If you have no running water you can’t flush toilets!)
Growing up in Minnesota I lived near a large beautiful freshwater lake. Today I live near a large river. Perhaps this is why I have a greater appreciation and awareness of fresh water. In college and as a gardener I learned many important lessons about soil and water. I remember witnessing what happens to water running over bare ground. The first “eureka” moment happened while I was watering a new flower garden. I had not yet mulched the garden and as I sprayed the bare soil the water quickly began to collect on the surface and run off. A few days later after covering the soil with mulch I was watering again. This time none of the water ran off. Rain drops and water spray disturb clay particles on the surface of the soil which causes the surface to seal preventing water from moving into the soil. Mulch (and plants) that cover the ground protect soil structure and keep it open allowing water to infiltrate. When water runs off the ground instead of soaking in it is not providing moisture for plants or refilling groundwater. Run off also carries soil particles and nutrients resulting in soil erosion and water pollution that degrades farmland and surface water.
Humans have not only changed earth’s climate because of atmospheric emissions from the burning of fossil fuels, we have also changed climate with our land management practices. Over the last 7,000 years of human history soil erosion, deforestation, overgrazing, neglect, and conflicts between cultivators and herdsman have helped topple empires and wipe out entire civilizations. “Conquest of the Land through 7,000 Years” is Dr. Lowdermilk’s personal report of a study he made in 1938 and 1939. You can download the report for free and it is well worth reading if you want to better understand the connection between soil, water, and human habitation of the land.
Lowdermilk describes in detail how deforestation and over- grazing reduces the cover of surface vegetation and leads to soil erosion and desertification. Humans have impaired the water cycle by cutting down forests, plowing up grasslands, and building cities (rooftops, paved streets and parking lots). We plant cropland with annual cereal grasses leaving the ground bare much of the year. Greenhouse gases are indeed warming the planet but a drying landscape is also increasing surface temperatures.
Vegetation cools the surface of land by intercepting solar radiation (which is used for photosynthesis) and by transpiring moisture from the ground. Humans sweat to cool our skin. Plants transpire moisture to cool their leaves. Evapotranspiration cools the earth’s surface because it takes energy to change liquid water into vapor. When water vapor in the atmosphere condenses and falls back to earth as rain the heat released by condensation occurs in the upper atmosphere. In the absence of vegetation, barren land simply absorbs sunlight and radiates the energy as sensible heat. (Deserts are much hotter than forests!) When we cause landscapes to dry the result is higher temperatures and drought, which further impairs vegetative growth. Plants requires ample soil moisture for growth. Our atmospheric emissions AND our land management practices are causing global warming, although as predicted the rate of warming has accelerated and climate change is reaching the point of emergency. The window to change habits in ways that may slow climate change is rapidly closing.
Agriculture has been a major cause of drier landscapes. For centuries we have drained wet lands in order to farm them. Even in the last ten years I have seen farmers installing drain tiles to dry the land more quickly in spring (mainly so that they can plant fields as early as possible). Even in an area that receives 40″ of rain annually farmers are starting to add center pivot irrigation in order to water crops during the hot, dry summer months. In draining the land they have reduced soil moisture preventing spring rains from soaking deeply into the ground to recharge local groundwater.
Groundwater fills the pore spaces between grains of soil and rocks. When we draw more water from an aquifer than is refilled the sediments (sand and gravels) are no longer saturated and the particles rearrange into a denser state, i.e. the pore spaces close. This effectively reduces air voids making it impossible to refill the aquifer as it once was. If the pore spaces close too much, they start to collapse, causing the land to shrink irreversibly. The resulting subsidence can be very dramatic as seen in this photo from California.
Urban development has also dried the land and reduced recharge. Cities were built along rivers to utilize waterways for transporting goods. Spring flood water once spread out across the land, but flooding has always been a problem for cities so we built levees and dams to control it. In the process we disrupted the natural function of flood plains impairing rivers as well as coastal estuaries that once received sediment. By draining urban streets as quickly as possible we are causing both disastrous floods, eutrophication of lakes, and ocean algal blooms. Even tropical storms are becoming more intense because moisture-filled air condenses over warmer ocean water rather than over land.
The bottom line is that removing vegetation from the land dries the landscapes and depletes aquifers. Forests and grasslands not only replenish the ground water but also bring rainfall. When we remove forests and plow up grassland we effectively dry out the landscape resulting in more severe droughts and floods. Bare soil absorbs and then re-radiates the energy as heat creating a desert where forests or grasslands once brought plentiful rain.
In my home state of Minnesota we proudly claim to be the land of 10,000 lakes, but the number of lakes are disappearing. Wetlands are disappearing. Theses maps show an enlarged section of the Missouri River Basin found in southwestern Minnesota. The maps below show changes in drainage since the 1860’s, when farming intensified. Forests were cleared and wetlands drained to create more farmland.
Most of the small farms I grew up with were diversified and self sufficient. They had wood lots and small ponds in addition to permanent pasture and meadows. This type of landscape offers many economic services that unfortunately isn’t factored into the cost of goods. Since they had no “value” they were simply destroyed, similar to burning Amazon forest to create cattle ranches and soybean fields.
Land rich with lakes, forests and grasslands offers plentiful food, clean and abundant water, and habitat for wildlife. It absorbs rain water and recharges ground water as opposed to running off to streams. Unfortunately the industrial farms growing industrial food suffers from short term thinking. The wetlands are gone and won’t recharge aquifers. The fields have become compacted, depleted in organic matter and cannot absorb as much rainfall as pastures. Confined Animal Feeding Operations (CAFOs) now replace small farm pastured livestock and pollute the water during times of flooding. This type of land management is certainly not sustainable. We must stop and reverse practices that continue draining the land, polluting the water, and over-pumping aquifers to irrigate crops that provide unhealthy food!
Across the world our management practices are depleting existing stores of groundwater at unsustainable rates. That means that we take out more than we allow nature to put in. “We’re running out of water, NASA images show more than half of the world’s largest aquifers are being depleted”. The water in many of the world’s aquifers is declining, dangerously, and unless we change irrigation and food production we may soon arrive at a future in which aquifers are depleted, snow and ice are gone, and cities will run out of water.
How do we increase the infiltration of water to recharge aquifers and prevent flooding disasters? The answer it turns out is pretty straight forward. Change your diet for one! Eat less manufactured food products and CAFO meat. We can also do things to keep water on the land and allow it to infiltrate. Flooding is worsened when we rush the water off the land. Wetlands, bioswales and rain gardens hold back water and allow it to infiltrate into the ground. When we develop land for municipal purposes we should require storm water detention ponds to hold water that runs off of rooftops and parking lots. Building sites can specify topsoil that is amended with compost to improve plant growth and infiltration. If we establish riparian zones (natural vegetation along rivers and estuaries) we can filter and clean water that does runoff the land. The most water absorbent landscapes are grasslands and forests. If we reestablish flood plains covered with living plants mainly trees and perennial grasses these surfaces will absorb many inches of rainfall per hour and prevent catastrophic flooding.
Bioswales are a relatively new feature in urban stormwater management. They are simply detention basins located along the street, filled with sandy soil and planted with grasses that slow runoff and filter it before it goes to the river. Pictured below is one of dozens of bioswales recently built in my community.
I have also built rain gardens at my home. A rain garden is simply a landscape feature that captures runoff using berms, mulch, and plants to keep water on the land and help it infiltrate rather than run off. The pictures show an area of my lawn that intercepts runoff from the land around our house, which sat on a hill.
At our new home I built a rain garden to capture runoff from the driveway. It is planted with native plants that also provide food for bees and butterflies. When we mulch and add organic matter to soil we improve the infiltration of water. When we establish native plantings, grasslands and forests we increase the capture of rainwater and improve groundwater recharge. Vegetation cools the local environment and provide habitat for wildlife. Shade trees cool our home and reduce energy use for air conditioning. Wind breaks reduces heating costs (and energy use). Cities with more green space are cooler, they have fewer impermeable surfaces and less runoff.
We need to improve the ability of watersheds to hold back the rain in urban and agricultural landscapes by supporting sustainable, regenerative agriculture, creating rain gardens, wetlands, ponds, and lakes. We need to think differently about rainwater and preserve it as much as possible so that the rain can add to our fresh water resources rather than runoff to the ocean. When we direct precipitation to rivers as quickly as possible we prevent water from replenishing soil and groundwater. As our planet continues to warm ice is melting and sea levels rising because the runoff is going to the oceans, not to the groundwater. Over time agriculture and urbanization have desiccated our environment, increased heat islands, and exacerbated flooding. In addition to generating greenhouse gases humans have developed landscapes in ways that are exacerbating the effects of global warming. If we don’t change, the frozen water will melt and end up in the oceans and we will lose fresh water needed by life on earth.
We can’t always change government policies but we can change how we eat and how we manage the landscape around our homes. Healthy plants are able to draw carbon from the atmosphere, reduce warming, and have a positive impact on the water cycle. Spread out across the land we will see less desertification, catastrophic storms and flooding. A moist environment is always much cooler than a dry one. Water that moves through the soil to the aquifer or discharges to surface water (rivers and lakes) is filtered and cleaned of pollutants. Add up all these benefits and we can begin to see the direction we must take if we want to limit disastrous climate change impacts and provide water resources necessary for life.