Water quality,trend detection,and causality

This paper begins by discussing the detection of a trend in water quality time series. Using the method of Box and Jenkins, an example of trend identification in sediment loading in the Iowa River is presented. Subsequent to the identification of a trend, an approach is suggested whereby the factors giving rise to the trend can be detected. For the example being considered, it is indicated that the cropping practices in the watershed have a significant impact on the detected trend. Thus, each 1% increase in the area of corn and soybeans planted results in about a 0.42% increase in sediment loading.