Water quality (resources and drinking water) is an ongoing challenge, particularly in the Lagoon and in the southern part of the region. Although the region has relatively abundant water, degradation in water quality in some parts of the city-region, notably the south-west, is a problem, and has resulted in water stress in some areas, and high demand in some spots has negative ecological consequences, particularly on smaller rivers and streams. Of particular concern are climate-change-related increases in mean sea level, and increased frequency of extreme storm surges in the Adriatic, which are associated with the highest water levels in Venice.