Freshwater inflows to Texas bays and estuaries: hydrology, circulation, and salinity data (1977-2018)

Patterns of freshwater inflow and salinity are presented for the Sabine-Neches, Trinity-San Jacinto, Colorado-Lavaca, Guadalupe, Mission-Aransas, Nueces, and Laguna Madre estuaries of Texas. There is a strong precipitation gradient from west to east, which translates into a strong freshwater inflow gradient where estuary inflows generally increase from west to east. There is a strong correlation between inflows of adjacent estuaries. Another driver of inflow is a cycle of extreme droughts and floods. Inflows to each estuary are highly variable, with the standard deviation of monthly inflows exceeding the mean in all estuaries except the Sabine-Neches. Seasonal patterns of inflows exist, with the easternmost estuaries (Sabine-Neches and Trinity-San Jacinto) exhibiting high inflows during winter and spring, mid-coast estuaries (Colorado-Lavaca and Guadalupe) having high spring and fall inflows, and lower coast estuaries (Mission-Aransas, Nueces, and Laguna Madre) having higher fall inflows, and lower coast estuaries (Mission-Aransas, Nueces, and Laguna Madre) having higher fall inflows. Freshwater inflow patterns create similar patterns in salinity, although salinity is complicated by the estuaries having differing volumes, tidal passes, and tidal prisms. In general, the Sabine-Neches Estuary is often oligohaline, whereas the Nueces Estuary and the Laguna Madre are often euhaline to hyperhaline, and the intervening estuaries are mesohaline and polyhaline. In most cases, salinity variability is highest where the salinity average is moderate in locations that swing between fresh and salt water. Near the Gulf passes, and near freshwater sources, the average salinity is high, and low, respectively, but the standard deviation is relatively low. More salinity monitoring and a more modern approach to salinity modeling is needed. Long-term trends are uncertain because of high spatial and temporal variability of inflow and salinity.