The aesthetic quality of water resources is often assumed to be valuable to society, yet few robust estimates of this value have been reported in the limnological literature. Because entire lakes and rivers are not bought and sold regularly, their aesthetic value cannot be determined by differences in market prices. Therefore, economically valid estimates must be determined by methods that estimate willingness to pay (WTP) for aesthetic value. Methods for and example results of an environmental valuation study to estimate local residents' and visitors' WTP for improved aesthetic quality in Clear Lake (Iowa, USA), a eutrophic, natural lake, are presented. Both revealed-preference and stated-preference techniques for estimating value are considered. In the revealed-preference application, WTP is inferred by comparing the number of times survey respondents planned to visit the lake given its current conditions with the number of times they would plan to visit if the lake's water quality were improved. In the stated-preference application, WTP is inferred by presenting survey respondents with a hypothetical ballot initiative offering improved water quality and resulting higher taxes associated, then estimating the highest tax bill at which the ballot initiative would have passed.