A visual approach for water quality monitoring within the CrowdWater project

CrowdWater is a citizen science project that uses a mobile phone application (app) to collect hydrological data. The project aims to develop and test methods for hydrological measurements that do not require sensors. So far, the app is used to collect data about stream water levels, the state of intermittent streams, soil moisture, and plastic pollution. The app can also be used to record general characteristics of streams, such as the color, the presence of fish and other living beings, or water pollution.

Perhaps without realizing it, many people make visual water quality assessments for their daily decisions. Based on visual aspects of the water, people decide whether the water is suitable for swimming or drinking. This presents an opportunity to explore the potential of a visual approach through citizen science-based water quality observations. Water color and clarity are one of the most frequently used indicators for the visual assessment of water quality. Remote sensing studies have shown that water color is changing in many areas, which suggests that it is useful to characterize visual water quality aspects throughout time and to relate these to perceptions of water quality and how this affects water use. However, most of the time this perception is not just based only on the current characteristics of the water but also on local environmental knowledge, such as the presence of outlets that discharge waste water or sewage overflows, the water quality in the past, etc.

This presentation will describe the visual approach for water quality that fits within the CrowdWater philosophy of not using any sensors so that observations can be made by anyone at any place. We will also present a first evaluation of the method. This includes discussing how consistent people are in their assessment of water color and whether they can assess differences in water color over time or between sites.