Satellite-assisted monitoring of water quality to support the implementation of the Water Framework Directive

The EU Water Framework Directive1 (WFD) is an ambitious legislation framework to achieve good ecological and chemical status for all surface waters and good quantitative and chemical status for groundwater by 2027. A total of 111,062 surface waterbodies are presently reported on under the Directive, 46% of which are actively monitored for ecological status. Of these waterbodies 80% are rivers, 16% are lakes, and 4% are coastal and transitional waters. In the last assessment, 4% (4,442) of waterbodies still had unknown ecological status, while in 23% monitoring did not include in situ water sampling to support ecological status assessment2. For individual (mainly biological) assessment criteria the proportion of waterbodies without observation data is much larger; the full scope of monitoring under the WFD is therefore still far from being realised. At the same time, 60% of surface waters did not achieve ‘good’ status in the second river basin management plan and waterbodies in Europe are considered to be at high risk of having poor water quality based on combined microbial, physical and physicochemical indicators3

Klimaatbestendige steden: drijvend bouwen: eerste onderzoeksresultaten ‘effect van drijvende constructies op waterkwaliteit’

Drijvend bouwen geniet in Nederland en internationaal veel aandacht. Gezien de relatief nieuwe ontwikkelingen is er echter nog weinig over de langdurige effecten op bijvoorbeeld waterkwaliteit bekend. Vanwege internationale kansen en kennisvragen is eind 2013 een onderzoek gestart naar de effecten van drijvende woningen op de waterkwaliteit met de focus op mitigerende maatregelen om de ontwikkelingen verder te stimuleren

Weinig invloed op ecosysteem onder drijvende objecten

Een grootschalig opgezet onderzoek, waaraan Nederland deelneemt, laat zien dat de ecosystemen onder drijvende objecten nauwelijks worden benadeeld door bijvoorbeeld de beperkte lichttoetreding. Vervolgonderzoek richt zich op het leggen van verbanden tussen de ecoscans en waterkwaliteitmetingen en de dimensies en bouwmaterialen van de constructie

Biomanipulation with quagga mussels (Dreissena rostriformis bugensis) to control harmful algal blooms in eutrophic urban ponds

Many urban ponds in The Netherlands and other countries suffer from eutrophication, resulting in harmful algal blooms which are often dominated by cyanobacteria. A sufficient reduction of nutrients, as prerequisite to mitigate cyanobacterial blooms in urban ponds, is not always feasible. Water managers are in need for applicable alternatives to mitigate these cyanobacterial blooms. The quagga mussel (Dreissena rostriformis bugensis) is a rapidly expanding bivalve species in many standing waters and rivers in The Netherlands. Because quagga mussels feed on algae, they could become a useful tool in controlling harmful algal blooms in urban ponds if provided with the appropriate substrate. We tested the hypothesis that quagga mussels can reduce phytoplankton biomass and induce a clear water state in a shallow hypertrophic urban pond. We executed an in situ enclosure experiment using eight enclosures (750 L) in an urban pond: four enclosures contained quagga mussels (0.3 g ww L-1), and four control enclosures were set up without mussels. We used artificial substrate for the breeding of mussels and the transfer from the breeding location to the experimental site. In contrast to the controls, the enclosures with mussels showed significantly lower concentrations of total chlorophyll-a (2.4 μg L-1 in mussel enclosures versus 84.1 μg L-1 in controls), cyanobacterial chlorophyll-a (1.0 μg L-1 versus 7.3 μg L-1) and total phosphorus (0.08 mg L-1 versus 0.17 mg L-1), and had higher transparency (>0.80 m in mussel enclosures versus 0.57 m in controls) and higher soluble reactive phosphorus concentration (0.03 mg L-1 versus -1). No effect of the mussels on microcystin concentrations was shown. The results show that quagga mussels are able to reduce the phytoplankton biomass in a hypertrophic urban pond, including cyanobacteria and induce a clear water state. We conclude that quagga mussels can be a promising tool in controlling algal blooms in urban ponds, in particular when a sufficient reduction of nutrients is not feasible. A preferred next step in the scaling up of the method is the determination of long-term effectiveness and side-effects in a controlled application in an urban pond. Because the quagga mussel is an invasive alien species, new introductions should be considered carefully and water purification using quagga mussels is preferably applied in water systems where the species is already present

Monitoring the impacts of floating structures on the water quality and ecology using an underwater drone

Urban delta areas require innovative and adaptive urban developments to face problems related with land scarcity and impacts of climate change and flooding. Floating structures offer the flexibility and multi-functionality required to efficiently face these challenges and demands. The impact of these structures on the environment, however, is currently unknown and research on this topic is often disregarded. This knowledge gap creates a difficulty for water authorities and municipalities to create a policy framework, and to regulate and facilitate the development of new projects. Monitoring the effects of floating structures on water quality and ecology has been difficult until now because of the poor accessibility of the water body underneath the structures. In this work, a remote controlled underwater drone equipped with water quality sensors and a video camera was used to monitor dissolved oxygen near and under floating structures. The collected data showed that most water quality parameters remain at acceptable levels, indicating that the current small scale floating structures do not have a significant influence on water quality. The underwater footage revealed the existence of a dynamic and diverse aquatic habitat in the vicinity of these structures, showing that floating structures can have a positive effect on the aquatic environment. Future floating structures projects therefore should be encouraged to proceed