Thursday, August 10, 2017

Climate Change, Rain and Nutrient Pollution

According to the National Oceanic and Atmospheric Administration (NOAA) global temperature has risen about 1 degree Celsius from pre-industrial times. Last year, reported to be the warmest year on record, was also the year that representatives from more than 175 countries gathered at the United Nations on Earth Day to sign the Paris Climate Accord.

The current administration has withdrawn the United States from the agreement. Even with the United States the Paris Accord lacked any clear path on how the nations would meet the goal to maintain global temperatures within 2 °C increase above pre-industrial temperatures. The carbon reductions committed to under the agreement are woefully inadequate to meet that goal, and neither China nor India who combined represent about a third of world greenhouse gas emissions have committed to any reductions. Instead those two nations are merely projecting when (not even at what level) their greenhouse gas emissions will peak.

If climate change progress, (and really, there are no realistic plans to stop it) most climate models are forecasting a significant increase in precipitation in the northeastern corridor of the United States including Virginia. At least we’ll have water, but all that rainfall can bring other problems. Rainfall and other precipitation washes nutrients from human activities like agriculture, lawns, septic systems and other activities into rivers and lakes. When these nutrients overload waterways, a process called eutrophication occurs. The results of this process can be dangerous to water quality when toxin-producing algae blooms develop and low-oxygen dead zones develop. We are all familiar with the annual dead zones and algae blooms in coastal regions including the Gulf of Mexico, the Chesapeake Bay and Florida.

In a recent study published in Science magazine Dr. Sinha and Dr. Michalak used models to predict how climate change might affect eutrophication. The two build on their earlier work where they found that, while land use and land management control the supply of nitrogen, precipitation controls how much of that nitrogen flows from the land into waterways. More rain more nitrogen and phosphorus pollution flows into waterways and estuaries.

In the current study, the scientists used these insights to predict how future changes to precipitation caused by climate change will, in and of themselves, affect nitrogen runoff and thereby increase the risk of water quality impairment in the United States.

Their modeling found that the mean projected increase in nitrogen loading within the continental United States is projected to be 19% with the Northeast projected to increase 28% and the Upper Mississippi Atchafalya River Basin project to increase 24%. In the Chesapeake Bay Watershed, the EPA has mandated a contamination limit called the TMDL (total maximum daily load) for nitrogen, phosphorus and sediment. The TMDL sets a total limit for the entire watershed of 185.9 million pounds of nitrogen per year which is a 25% reduction in nitrogen from 2011 levels. Increased rainfall will make meeting and maintaining those goals more challenging.

So far Virginia is on track to meet the midpoint goals for nitrogen reduction set by the EPA. We did it by having spent about $2 billion from 1998-2017 to upgrade the waste water treatment plants in the watershed. That was expensive, but easy to achieve reductions- we knew how to do it.

The remaining areas for reducing nitrogen for the midpoint evaluation and the 2025 goals are in the agricultural, suburban and urban storm water management. These are harder targets to hit because the sources of pollution in these areas are non-point source pollution (NPS), diffuse sources of pollutionthat are carried to streams and rivers by runoff of rain and snowmelt.

The way to reduce non-point source pollution in the environment is to control stormwater and implement what is called “best management practices” (BMPs). BMPs have mostly been used in the agricultural sector. Virginia made great progress towards the EPA goal in management of livestock. A huge program carried out by the Soil and Water Conservation Districts to induce all animal operations to fence all pastures to exclude all livestock from rivers and streams and provide alternate sources of water for the animals away from rivers and streams. There are also BMP to slow storm water, limit fertilizer use and limit or eliminate tilling.

To protect our waters with the forecast increase in precipitation the Soil and Water Conservation Districts will have to introduce programs for suburban neighborhoods and communities and keep improving and expanding those programs. We can’t stop the rain, but we can prepare for it.

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