This report summarizes the main results from a choice experiment survey addressing peoples’ willingness to pay (WTP) for improvements in surface water quality as well as groundwater quality. A particular novel focus is on estimating the extent to which WTP is impacted by the time lags and outcome uncertainties that commonly occur in practice when implementing new policies to improve water quality. The survey is conducted across four different case areas in four different countries, involving responses from more than 3000 respondents. Results generally confirm previous findings that people on average have quite high WTP for improvements in water quality, both in relation to surface water and groundwater. In addition, the results show that the WTPs reduce significantly with increasing time lags and outcome uncertainty in relation to the actual water quality improvements.