The Salton Sea is a shallow inland lake located in the southeastern border of California. Climate change and decreasing inflowing water have caused its elevation to drop gradually and more lakebed to expose. The exposed lakebed is a significant source of dust emissions and particulate matters, which consequently has a great impact on the health of nearby residents. To monitor the gradual shrinkage of the Salton Sea, this paper develops a change-point-detection chart for detecting process mean drifts. The proposed chart is based on the generalized likelihood ratio statistic with the unknown drift size estimated by an exponentially weighted least square regression procedure. Numerical studies show that it is effective for detecting process mean drafts. Application of this method to monitoring the gradual shrinkage of the Salton Sea using the observed Landsat images of the Salton Sea region is discussed in detail.