IOWA’S STATEWIDE WATER QUALITY SENSOR NETWORK: QUANTIFYING IOWA’S N EXPORTS 2016-2017

Evaluating progress toward statewide water quality goals, such as those set by the Iowa Nutrient Reduction Strategy, is inherently difficult due to the extensive and large scale nature of monitoring and assessment required. Recent advances in water quality sensor technology, like that of real-time, in-situ, continuous UV nitrate sensing techniques, have greatly increased our ability to quantify N loads exported from Iowa. Here, we use data from the Iowa Water Quality Sensor Network to evaluate N loads delivered to the Mississippi–Atchafalaya River Basin (MARB) from Iowa during the 2016-2017 monitoring years. Data acquired during 2016 monitoring, show a statewide average NOx-N concentration of 8.7 mg/L, averaged from all available sensors. N yields draining to the Missouri River were estimated to be 35.7 kg/ha, and 31.4 kg/ha from catchment tributaries draining directly to the Mississippi River. Iowa’s calculated N contribution to the MARB is higher than that estimated in previous studies, at 477 million kg N or 41% of the N load delivered to the MARB during the year 2016. Data generated from 2016 monitoring is compared to the newly collected 2017 dataset and a summary of year-to-year trends is discussed. Nitrate and other water quality data from the Network is made publicly available in through the Iowa Water Quality Information System (https://iwqis.iowawis.org/).