Assessing the relationship of background factors governing the water quality of an agricultural watershed with changes in catchment property (W-Hungary)

- Agricultural watershed assessed.
- Dynamic Factor Analysis (DFA) used.
- Contribution of point source and diffuse nutrient loads separated.
- Driving factors of water quality determined.

SummaryWith urbanization and the growth of agriculture, the importance of precisely assessing the contribution of diffuse- and point source loads arriving to surface waters is becoming more and more important. Determining their effects, however, is not as straightforward as it at first seems. The main aim of the study was to determine the driving background factors of a river located in an agricultural watershed, and furthermore, to separate the role of the diffuse- and point source nutrient loads. The method used to achieve the aims was Dynamic Factor Analysis. This is an effective tool for exploring time series which describe such phenomena. It is capable of taking into account the lagged correlation structure, thus enabling the researcher to uncover the background processes operating in time series. Dynamic Factor Analysis was applied to the time series (1978-2006) of 21 response parameters measured in the River Zala and 6 explanatory (agricultural, meteorological, water quality, etc.) parameters measured in its watershed.The results demonstrated that with the aid of Dynamic Factor Analysis the superimposed effects of the socio-economic changes which began in the mid-1980s, and the introduction of advanced wastewater treatment (P removal) in the river catchment in the early 1990s could be separated and their relative importance assessed, as well as that of other determining external factors.