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This indicator allows for an assessment of the impact of human development on ambient water quality, as well as the potential to obtain future ecosystem services from the water body (for example, drinking water production and biodiversity.

The indicator is defined as the proportion of water bodies in the country that have good ambient water quality. Ambient water quality refers to natural, untreated water in rivers, lakes and groundwaters and represents a combination of natural influences together with the impacts of all anthropogenic activities. The indicator relies on water quality data derived from in situ measurements and the analysis of samples collected from surface and groundwaters. Water quality is assessed by means of core physical and chemical parameters that reflect natural water quality related to climatological and geological factors, together with major impacts on water quality. The continuous monitoring of all surface and groundwaters is economically unfeasible and not required to sufficiently characterize the status of ambient water quality in a country. Therefore, countries select river, lake and groundwater bodies that are representative and significant for the assessment and management of water quality to monitor and report on indicator 6.3.2. The quality status of individual water bodies is classified based on the compliance of the available water quality monitoring data for the core parameters with target values defined by the country. The indicator is computed as the proportion of the number of water bodies classified as having good quality (i.e. with at least 80 % compliance) to the total number of assessed water bodies, expressed as a percentage.

National Hydrological Service (NHS)

National Hydrological Service (NHS)

Quinquennial

Percentage (%)

Good ambient water quality is essential for protecting aquatic ecosystems and the services they provide, including: the preservation of biodiversity; the protection of human health during recreational use and through the provision of drinking water; the support of human nutrition through the provision of fish and water for irrigation; the enabling of a variety of economic activities; and the strengthening of the resilience of people against water-related disasters. Good ambient water quality is therefore closely linked to the achievement of many other Sustainable Development Goals. The methodology recognises that countries have different capacity levels to monitor water quality, with many developed countries operating extensive and complex program that collect and report data to existing reporting frameworks beyond the scope of this methodology. For these countries it is recognized that this methodology will not contribute to improving their water quality; however, it must be sufficiently flexible to capture data from existing monitoring frameworks without burdening countries with additional reporting obligations. Conversely, many of the least developed countries currently do not monitor water quality or operate very limited monitoring programmes. The methodology must therefore allow these countries to contribute to the global indicator, according to their national capacity and available resources.

Aquifer: Geological formation capable of storing, transmitting and yielding exploitable quantities of water.

Classification of water quality: If at least 80% of the monitoring values for prescribed parameters in a water body comply with their respective target values, the water body is classified as having a “good” water quality status. Each water body is classified as being of “good” or “not good” status.

Groundwater: Subsurface water occupying the saturated zone.

Groundwater body: A distinct volume of groundwater within an aquifer or aquifers (EU 2000). Groundwater bodies that cross river basin district (RBD) boundaries should be divided at the boundary with each separate portion of the groundwater body being reported separately along with its respective RBD.

Lake: Inland body of standing surface water of significant extent.

Non-point-source pollution: Pollution of water bodies from dispersed sources such as fertilizers, chemicals and pesticides used in agricultural activities.

Parameter: Water quality variable or characteristic of water quality, also called a determinant.

Point source pollution: Pollution with a precisely located origin.

Pollution (of water): Introduction into water of any undesirable substance which renders the water unfit for its intended use.

Transboundary waters: Surface or ground waters which mark, cross or are located on boundaries between two or more States; wherever transboundary waters flow directly into the sea, these transboundary waters end at a straight line across their respective mouths between points on the low water line of the banks (UNECE, 1992).

Water quality index: The measured water quality results for all parameters combined into a numeric value for each monitoring location. These scores are then aggregated over the time of the assessment period. The index score can range between zero (worst) to 100 (best).

is by water body type (river, lake, groundwater) and river basin district.

This disaggregated data can support informed decision-making at the national and sub-national scale to monitor and improve water quality management measures.

The indicator is computed by first classifying all assessed water bodies based on the compliance of the monitoring data collected for selected parameters at monitoring locations within the water body with parameter-specific target values:

The percentage compliance [%] = (the number of monitoring values in compliance with the target values / the number of monitoring values in compliance with the target values) * 100

A threshold value of 80% compliance is defined to classify water bodies as “good” quality. Thus, a body of water is classified as having a good quality status if at least 80% of all monitoring data from all monitoring stations within the water body are in compliance with the respective targets.

This indicator provides the Hydrology Unit with a mechanism for determining whether, and to which extent, water quality management measures are contributing to the improvement of water quality over time.

The monitoring and reporting of SDG Indicator 6.3.2 requires considerable national financial and human capacities to regularly measure water quality parameters at sufficient spatial and temporal resolutions, and to consistently collect, quality-assure and process the monitoring data to compute the indicator. Substantial investments in monitoring and data management infrastructures, as well as targeted capacity development in water quality monitoring program design and operation, will be required in many countries to enhance national capacities to regularly and consistently report on the indicator.

The recommended sources of data are water quality monitoring data derived from in situ measurements and the analysis of samples collected from surface and groundwaters in national or sub-national ambient water quality monitoring programmes implemented by governmental authorities. Additional water quality monitoring data from research or citizen-science monitoring programmes can be used to supplement the available authoritative monitoring data, provided they are authorised by the national reporting agency. 

All the metadata shown in this document was gather from United Nation Statistics. The meta data was extracted from https://unstats.un.org/sdgs/metadata/.