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Attachment B: Supporting Research Research Review Phase of the IRC Lagoon Management Plan: Update 1 1. Annual Rainfall Data Rainfall acts as one of the major contributors of freshwater into the Indian River Lagoon estuary system. It is important to monitor rainfall because of its impacts to the Lagoon, such as influencing salinity levels, increasing sediment runoff, and transporting other pollutants and nutrients from land to water. Excessive rainfall can cause flooding and damage to infrastructure such as stormwater or wastewater conveyance. The Lagoon, in its entirety, on average receives about 50 inches of rainfall per year, with the County's portion receiving approximately 52 inches per year. Annual rainfall data was gathered using the National Oceanic and Atmospheric Association's (NOAA) 16 historical and active weather stations across the County, with data from 1895 to present. The wettest months in the County historically have been June through September. Based on rainfall measurements, rainfall in the County is seeing an approximate decrease of 0.27 inches per decade. While we do not understand the specific, measurable impacts caused by this decrease, decreased rainfall in general impacts the Lagoon's inputs of freshwater. Salinity data will be examined during a future update, with the goal to better understand how rainfall and salinity levels combined affect the health of the Lagoon. 2. Best Management Practices Best Management Practices (BMPs) are practices deemed to be an effective and practicable means of preventing or reducing water pollution generated from various activities and industries. Stormwater and Utilities departments within the County both utilize BMPs for their water treatment systems, which act as regional scale BMPs. For example, Stormwater's Egret Marsh is a pollution control facility that uses algae, large ponds, and a man-made wetland system to remove excess dissolved nutrients from water withdrawn from stormwater canals each day before it reenters the canal system leading to the Lagoon. These regional scale BMPs are accounted for in Basin Management Action Plan (BMAP) reporting to the Florida Department of Environmental Protection (FDEP). Regulatory agencies determined that the Lagoon's water quality was impaired due to excessive amounts of phosphorus and nitrogen, as well as low levels of dissolved oxygen (DO), as evidenced by the decrease in seagrass distributions. In 2007, FDEP added the main body of the Lagoon to the Verified List of impaired waters, which established the creation of allowable loadings of phosphorus and nitrogen to the Lagoon, known as Total Maximum Daily Loads (TMDL). TMDLs are scientifically derived levels of constituents that a body of water can receive while still meeting water quality standards. BMAPs are then created after a TMDL has been set for a waterbody. BMAPs act as "blueprints" for restoring impaired waters by reducing pollutant loadings to meet the allowable loadings in a TMDL. BMAPs utilize various strategies, from permit limits on wastewater facilities to urban and agricultural BMPs, to reach these pollutant reduction goals. Limits, or allocations, are assigned to stakeholders, and those limits are enforceable. The County falls within the Central Indian River Lagoon BMAP for the Indian River Lagoon Basin. The BMPs the County implements in these regional -scale projects contribute to reduced pollutant loadings reported in this BMAP. The County enforces proper implementation of BMPs at construction sites, with the authority to issue citations of permit violations that can lead to fines and/or project shutdown. Education is also an 92