Drought!


The number of people that recall the Dust Bowl of the 1930s is dwindling and that may portend poorly for society (likewise the loss of Depression memories and two world wars).  The Dust Bowl was aptly names for the regular storms of windblown dust that pummeled farm fields and blew away valuable topsoil needed by farmers.  Why it occurred was more interesting and foretelling.

The amount of farming had exploded in the late 1920s as a result of  record wheat price, motorized tractors and government programs encouraging farmers to plow up the prairie and plant.  The crops replacing the native plants did not have the same root structure and were less drought tolerant as a result.  When wheat prices collapsed, the fields were left fallow exposing the topsoil to the elements.  Since the topsoil was no longer anchored to the soil by plants, the wind and lack of rain caused much of the topsoil to migrate with the wind as dust.  Topsoil was lost, rain ran off, transpiration decreased, and the cycle just go worse.   Up to 75% of he topsoil was lost.

Rains returned in the 1940s but much of the dry farming (no irrigation) practice was immediately converted to wet framing using deep wells to capture water from aquifers.  The result was healthier crops, more consistent yields and protection of the remaining topsoil as a result.  Or is it?

Visit California today.  They are in the midst of severe drought conditions. Farmers have attempted to protect themselves by drilling more wells – deeper wells which diminish water supplies to the shallower neighboring wells.  Water levels decline, land subsides, the aquifer collapses, and there is little recharge.  Some areas of the central valley have sunk over 8 feet in the past 100 years.  But we have up until this point, had healthier crops and more productive yields, which protects the valley until the rains return.  Or does it?

While the lack of rainfall is a natural cycle, there is an argument to be made that man-made impacts have exacerbated the situation.  In the Dust Bowl states, the initial error was plowing up the native grasses without understanding how they had adapted to the mostly dry conditions on the prairie.  Many of the prairie states receive under 20 inches or rain each year, and scarcely any during the summer, which limited evapotranspiration, which limits thunderstorm and regional rainfall activity.  Less ET = drier conditions.  So growing crops is not what one would immediately identify and a “normal” land use for the prairie.  We altered the environment, but the Midwestern farming thought process doesn’t work in the dry prairie.  Irrigation was needed, but the lack of surface water limited irrigation unless wells are used.  Wells were drilled which returned and improved crop yields, but the well use has caused massive decreases in aquifer levels in the prairie states. The amount of water is finite, so as long as withdrawal exceed recharge, and with only 20 inches of rain that mostly runs off the land, there is a point in time when the well runs dry.  As the well runs drier, productivity will fall.  The interim fix is drill deeper, but the bottom of the aquifer is in sight.  Then, fields will be fallow, agriculture will be impacted dramatically, and it is not inconceivable the Dust Bowl type conditions could reoccur. Policies by man exacerbate the problem because the prairie productivity is accelerated will above its natural condition.

Likewise much of the land subsidence problem in California is irrigation driven – water is pulled through wells in an ever increasing competition to maintain one’s crop yield.  Water wars and fights with one’s neighbors over wells drying up is increasing more common as irrigation needs increase and recharge to the aquifer is diminished.  Much of California is even drier than the Dust Bowl states, and more reliant or wells and irrigation.  Less water also means less ET which means less local rainfall.  So while California has done much to protect itself over the years from drought, the current experience says that declining aquifer levels means we have exceeded the productivity of that state as well.  So is the California Dust Bowl coming?

Man is an ingenious creature.  We overcome much that the Earth throws at us.  But at the same time, we rarely consider the consequences of our actions in overcoming the challenges Earth poses.  These two examples show how our efforts to solve one problem, may actually damage the long term sustainability of these areas.  Short term gain, long term problem.

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: