Land cover changes in the Tampa Bay watershed (Florida) over the past four decades were examined along with precipitation and wind observations to help understand causes of long-term changes in turbidity and chlorophyll concentration within the Tampa Bay estuary. Water quality showed a statistically significant relationship to land cover fraction in the watershed compared to long-term precipitation or wind stress. Redundancy Analyses with Akaike's Information Criterion and non-parametric multiple regressions determined that turbidity and chlorophyll concentration decreased bay-wide from 1974-2012 with increased developed land fraction (R 2  > 0.75, p-value < 0.05). Various segments of the estuary showed different significant responses to developed land (R 2  > 0.75, p-value < 0.05), agricultural land (R 2  > 0.93, p-value < 0.02), bare land (R 2  = 0.77, p-value = 0.001), and wind stress (R 2  = 0.91, p-value = 0.04) at different times of year.