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Regional Trends

Monitoring Surface Water Chemistry | TIME/LTM | Current TIME/LTM Regions | Map of Sites

The Temporally Integrated Monitoring of Ecosystems (TIME) and Long-Term Monitoring (LTM) networks provide information on the chemistry of lakes and streams to indicate how water bodies are responding to changes in SO2 and NOx emissions. The data presented in the graph show regional trends in acidification from 1990 to 2006 for LTM network sites. For each lake or stream in the network, measurements of key indicators of recovery from acidification were plotted against time and trends were calculated for period (1990-2006). Using the trends calculated for each water body, regional trends were determined (as the median slope value for the trends in all the sites in the region) for each key indicator. A negative value of the "slope of the regional trend" means that the measure has been declining in the region, while a positive value means it has been increasing. The greater the value of the trend, the greater the yearly change in the measurement recorded. Movement toward recovery is indicated by positive trends in acid neutralizing capacity (ANC) and negative trends in sulfate and nitrate. Source: EPA 2008

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