How can negative effects on water quality be countered?

In many cases, climate change is exacerbating existing problems, but it can also cause new problems. To counter any negative effects of climate change or of adaptation measures on water quality, measures may need to be taken. But which? This page contains several tools that will help you select appropriate measures.

Water quality measures can be intended to improve water quality and aquatic life. In addition, they can be intended to improve the functional quality of urban water, for example, for use as drinking water or industrial process water.→ Read more about the impact of climate change on water quality and aquatic life→ Read more about the functional uses of surface water and how these are affected by climate change

Ecological system analysis based on Key Ecological Factors and Guide to Water Quality Stress Tests

The implementation of appropriate measures for clean and healthy water requires a customised approach. First, you need to understand what exactly is wrong with a water system. Important questions are, for example: what does the water system look like and how is it situated in the landscape? Which common issues are prevalent, such as pollution or drought? What is the current condition of the water?

  1. The ecological system analysis based on the Key Ecological Factors helps to provide insight into the matter. The idea is that truly effective measures can only be taken on the basis of a proper understanding of how the system works. Otherwise, you will run the risk of a measure failing to resolve the problem. More information on the ecological system analysis based on Key Ecological Factors is provided on the website of the Foundation for Applied Water Research (STOWA).
  2. To factor in the impact of climate change, the Guide to Water Quality Stress Tests has been developed. This guide ties in directly with the ecological system analysis based on Key Ecological Factors. Conducting such a stress test will show where the water system is vulnerable to climate change and what is causing such vulnerability. The stress test can produce both qualitative and quantitative insights. When determining which measures to take, you will need both types of information. For example, are you seeking to reduce the nutrient content of the water? Then you will need to calculate both the maximum proportion of nutrients the water may contain (quantitative) and which source is contributing most to the problem (qualitative). The “stress test meta model” is a calculation tool that will be helpful in this respect.

Overview of water quality measures

Measures to improve water quality can vary widely. For example, a measure such as reaching out to swimmers regarding blue-green algae is quite different from measures involving adaptation of the sewer system or a reduction of emissions from buildings. Are you looking for ideas or inspiration for measures? These two tools can help you on your way:

  1. Water Quality Roadmap measures: this online tool can be used to compile an overview of potential measures, based on information regarding an area. The tool shows measures tackling the issue at its roots and measures focused on its impact reduction. The roadmap can be used for freshwater systems in both urban and rural areas.
  2. The interactive knowledge document on Urban Water Quality, Climate and Adaptation (pdf, 13 MB) has been developed especially for urban areas. The last section (starting on page 156) addresses measures to improve water quality. For clarity’s sake, the measures have been divided into clusters. For each cluster, a brief explanation is provided, with several photos of measures. This can provide inspiration to reflect on ways to make the water system more resilient. To find out how the various measures impact the indicators, you can take a look at the Table of water quality measures (xlsx, 32 kB). The overview of measures is not exhaustive.

Management and maintenance

The measures in the “Management and maintenance” cluster are focused on the management and maintenance of the water system. They involve, for example, mowing management regimes, dredging management regimes and weed control.

  • Dredging watercourses: the layer of mud on the bottom of ditches, canals and lakes is regularly removed for various reasons, for example, to give the water more room;
  • Keeping off birds and/or implementing a feeding ban;
  • Environmentally friendly weed control;
  • Removal of waste near trash screens, culverts or weirs;
  • Removal of leaves on river banks;
  • Clearing away blue-green algae;
  • Flushing the water after sewer overflows;
  • Removal of duckweed from the water;
  • Intensive water plant management;
  • Removal of leaves from the water.

Water chain

The measures in the “Water chain” cluster address the actual water chain and involve, e.g., adjustments to the sewer system or changes in flushing regimes.

  • Creating a bioswale or soil passage to disconnect paved surfaces from the sewer system. Bioswales are primarily intended to slowly drain water into the soil, whereas soil passages are mainly intended to filter the water;
  • Installing a storage settling basin or filters at sewer overflows, to prevent dirt ending up in surface water;
  • Detecting faulty sewer connections.

Hydrological functioning

The measures in the “Hydrological functioning” cluster improve water behaviour and characteristics, for example, by allowing free flow or enabling the intake of clean water.

  • Modifying intake regimes: adapting the frequency or rate of water intake from another watercourse;
  • Taking in water from another source;
  • Removing phosphates from inlet water;
  • Relocating inlets to freshwater locations;
  • Expanding a culvert to optimise the connection between two watercourses;
  • Raising or lowering a culvert to optimise the connection between two watercourses;
  • Connecting bodies of water, for example, by constructing a culvert;
  • Restoring seepage effect (fresh water): restoring freshwater seepage from the soil.

Structure

The measures in the “Structure” cluster adapt the water system profile. For example, a water system can be rendered deeper or shallower. Another example is interconnecting multiple bodies of water.

  • Getting rid of dog walking locations;
  • Creating a buffer zone between a road and a watercourse;
  • Providing collection points for emptying marine toilets;
  • Making water deeper;
  • Making water shallower;
  • Planting hedges on river banks;
  • Planting trees on river banks;
  • Fostering water circulation;
  • Granting or revoking permits for cold water discharge and/or warm water collection;
  • Installing a fountain or bubble screen to aerate the water, in order to boost its oxygen content.

Communication and acceptance

Issues resulting from deteriorating water quality cannot always be prevented. In such cases, clear communication with water consumers is helpful. Another measure could be accepting that a particular use will not always be possible.

  • Communication on hygiene regulations;
  • Communication on health risks of swimming and other water leisure activities;
  • Acceptance of issues such as stench or fish mortality;
  • Acceptance of changing ecological quality.

Alternative uses

The water quality may have deteriorated to such an extent as to preclude certain functions. In such cases, measures could be considered to switch to alternative functions.

  • Harvesting duckweed: a new method of producing protein;
  • Farmers in salinised areas may switch to saline crops, which are irrigated with saline water in addition to freshwater.

Explanation of the table

The table is intended as a source of inspiration to spark a dialogue on the most effective ways to boost the resilience of the water system. In the table, the measures are also subdivided into clusters. They have also been categorised into three types of measures. Furthermore, the table shows the scale level at which a measure is implemented and by which party (the initiator). For example, “Dredging a watercourse” is a local measure, carried out by a municipality and/or district water board. On the right-hand side, the indicators are listed, followed by two types of measures: effect-oriented and source-oriented. The “source-oriented measures” list the control variables corresponding to the indicator. The squares indicate the indicators or control variables that will increase or decrease as a result of the measure. This increase (T) or decrease (A) is usually positive (green), but in some cases, it may be negative (red).

Explanation of types of measures

The measures in the table are categorised in three types: prevention, adaptation and acceptance. These categories are explained below.

  1. Prevention: measures that prevent further deterioration of the water quality. For example, filtering water containing micro pollutants before run-off; disconnecting downspouts to prevent sewer overflows; or constructing a buffer system in areas dependent on river water.
  2. Adaptation: measures that mitigate any negative effects of climate change. For example, more frequent flushing of deteriorating surface water; or providing shade around surface water.
  3. Acceptance: measures to accept a change in or deterioration of the water quality. For example, by capitalising on opportunities opened up by such changes, such as switching to saline crops. Or by raising awareness of risks to encourage changes in human behaviour, such as communicating on blue-green algae at non-official swimming locations, to prevent people from going for a swim there.

Effect-oriented and source-oriented measures

The table below the indicators distinguishes between effect-oriented measures and source-oriented measures:

  • The effect-oriented measures are intended to reduce the impact of climate change. They affect an indicator as a whole.
  • The source-oriented measures are intended to remove the source of negative effects. These measures affect specific control variables.

For example, “Clearing away blue-green algae” targets the effect of directly improving the indicator of nutrient content and does not address any of the sources of excessive blue-green algae growth. “Removal of leaves from river banks”, on the other hand, addresses a source of excessively high nutrient content in surface water. That is why the box indicating the Leaf Fall control variable in the table is coloured green and marked with an A, as the measure will reduce leaf fall.