AGRICULTURE'S IMPACT ON WATER QUALITY: A CEDAR RIVER AND MISSISSIPPI RIVER ANALYSIS

The Dead Zone, a coastal hypoxic area at the mouth of the Mississippi River in the Gulf of Mexico, results from excess nutrients carried by the Mississippi River. A primary source of these excess nutrients is agricultural land from nutrient fertilizers, manure, and surface runoff. Previous research has established that the dominant origin of excess nutrients contributing to the hypoxic area is traced back to the upper Mississippi River basin, including the Cedar River in eastern Iowa. Building upon this foundation, this research examines the spatial and temporal patterns of water quality from the upper Cedar River to its integration into the Mississippi River. The distribution of stream water quality in the Cedar River and Mississippi River is influenced by various factors such as local land use practices, including agriculture, and the steam’s unique hydrological characteristics. Results demonstrate a gradual increase in total suspended solid (TSS) levels downstream from site 1 (17.13 mg/L) to site 7 (43.63 mg/L), attributed to an expanding drainage basin with increasing runoff carrying sediment downstream. The declining levels of nitrate, a form of nitrogen pollution, from site 1 (21.10 mg/L) to site 7 (5.73 mg/L) can be related to the decrease in agricultural land and an increase in municipal and industrial land draining into the river. Temporal distribution analysis highlights seasonal changes in water quality into the fall. Decreased levels of TSS from early September (41.61 mg/L) to October (21.55 mg/L) is associated with decreased agricultural harvesting and farming activities disrupting sediment in the river’s catchment. Nitrate levels decreased from September (22.09 mg/L) to October (9.41 mg/L) as the fall season progressed correlated with declining agricultural activities that employ fertilizers onto agricultural land. These findings highlight the complex interplay of agricultural, industrial, and seasonal factors that have broad implications for understanding the intricate dynamics of water quality in the Cedar River and the wide-reaching Mississippi River basins. By identifying the distribution and patterns of water contamination, this research contributes to informed decision-making for sustainable agricultural and land use practices.