The Gulf of Mexico dead zone — an oxygen-starved area that can kill fish and marine life — is larger than scientists forecast in June, the National Oceanic and Atmospheric Administration reported Tuesday.
The larger size was caused by heavy June rains throughout the Mississippi River watershed, NOAA said. The size — 6,474 square miles — is about the size of Connecticut and Rhode Island combined.
This year’s measurement is larger than last year’s 5,052 square miles, “indicating that nutrients from the Mississippi River watershed are continuing to affect the nation’s coastal resources and habitats in the Gulf,” NOAA reported.
Hypoxia occurs when nutrients, primarily nitrogen and phosphorus, “stimulate an overgrowth of algae that sinks, decomposes and consumes the oxygen needed to support life in the Gulf,” NOAA said.
The Mississippi River-Gulf of Mexico Watershed Nutrient Task Force hoped to reduce the Gulf dead zone to 1,900 square miles. The group includes five federal agencies, 12 states including Iowa, and tribes within the river basin draining into the Gulf.
The group has been criticized for failing to significantly reduce the nutrient runoff from agriculture, businesses and cities that contribute to the Gulf dead zone.
Iowa’s Nutrient Reduction Strategy, adopted in 2013, encourages Iowa farmers to embrace conservation practices that will help improve water quality in the Gulf as well as Iowa. It also targets nutrients that come from wastewater treatment and industrial plants.
Among the strategy’s critics is Des Moines Water Works leaders, who have blasted the plan as ineffective in helping to reduce nutrients that pollute Iowa waterways.
The utility sued three rural Iowa counties, saying drainage districts in Sac, Calhoun and Buena Vista counties act as a conduit for nitrogen to move from farm fields into the Raccoon River, one of two sources of drinking water for 500,000 residents.
Water Works seek federal regulations that would force the districts, and indirectly farmers, to adopt conservation practices.
Farm leaders have said several factors affect nitrogen and phosphorus levels in Iowa water, including the amount of rain received during the year. They say regulations provide no assurance that water quality in Iowa or the Gulf will improve.
NOAA said the Gulf of Mexico dead zone is the second-largest human-caused hypoxic area in the world, which has a total of about 550.