S30

Riparian habitats represent an important ecosystem providing a number of functions and services that are important to humans - such as promoting biodiversity, reducing erosion risk, or transporting pollutants from the surrounding landscape into waterways. At the same time, unfortunately, it is an environment that has very often come under considerable pressure as a result of agricultural cultivation of the landscape or the development of industrial and human settlement activities. Thus, a large number of riparian ecosystems have disappeared or deteriorated. The assessment of the overall ecological status of riparian habitats is therefore an important source of information for the needs of water management and landscape planning in the riparian landscape, the aim of which should be to maintain the good status or improve the currently unsatisfactory status of these habitats. In the Czech Republic, there is not yet a comprehensive assessment procedure that takes into account not only the important sub-variables that influence the current status (e.g. the morphological condition of the watercourse or the predominant land use categories in the surrounding area), but also the potential reference status. For this reason, a tool (Riparian Habitat Quality Index) was developed by the author's team to assess the ecological status of riparian habitats. The created web platform "RipaSoft" allows streamlining the whole assessment process. Our contribution describes the assessment procedures and selected results of applying the methodology to several case study sites (small stream watersheds). The results can significantly contribute to the identification of sites suitable for the implementation of nature-based solutions aimed at mitigating vulnerability to hydrological risks (not only the risk of droughts and flash floods, but also the pollution of surface waters due to the transport of fertilizers and other pollutants from the surrounding landscape).

How to cite: Jakubínský, J., Cudlín, P., Pechanec, V., Machová, K., Cudlín, O., Štěrbová, L., Purkyt, J., and Prokopová, M.: Riparian zone assessment as a tool for planning nature-based solutions, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-174, https://doi.org/10.5194/iahs2022-174, 2022.

Nutrient pollution is among the biggest water quality challenges facing environmental engineers, causing ecosystem health decline and requiring significant treatment before water is safe for human use. The remediation of nutrient pollution can occur along the river corridor where nutrients can be retained and transformed to environmentally benign products (e.g. N₂) by microbially mediated reactions. Catchment mismanagement, especially the removal of wood from channels, has reduced the capacity of rivers to fulfil this function, limiting reactions by two primary mechanisms: transport and reaction kinetics. These limitations could be abated by restoring rivers with instream wood, thereby providing a Nature-based Solution to this persistent water quality challenge.

Little research has directly investigated the potential of wood introductions to increase nutrient transformations in the river corridor. Here, we present results on two linked experiments which investigated the transport and reaction kinetics of nutrients at different scales.

The transport limitation refers to the total flux of water into the hyporheic zone, a hotspot of biogoechemistry in the river sediment, and its residence time therein. Instream wood causes an obstacle for river flow which could induce hyporheic exchange of suitable properties to allow favourable nutrient transformations. To investigate this, we installed wood features in a lowland stream in the UK and conducted a series of smart tracer injections to estimate (metabolically active) transient storage using a powerful before-after-control-intervention experimental design.

The reaction kinetic limitation refers especially to the availability and quality of organic matter, which could be improved by wood decomposition. An incubation experiment investigates the potential of instream wood as a source of organic matter and the effect of this on nutrient transformation rates and greenhouse gas production.

Preliminary analysis suggests that wood is effective at increasing nutrient transformations in both mechanisms. In the incubation experiment, nutrient transformation rates were higher in systems with wood compared to those without. In the field experiment, more metabolically active transient storage was observed in the sub-reach where restoration features had been installed. Our results provide evidence for the effectiveness of wood in river restoration and the efficacy of Nature-based Solutions for water quality challenges.

How to cite: Howard, B., Baker, I., Kettridge, N., Ullah, S., and Krause, S.: Restoring instream wood as a Nature-based Solution to nutrient pollution, IAHS-AISH Scientific Assembly 2022, Montpellier, France, 29 May–3 Jun 2022, IAHS2022-704, https://doi.org/10.5194/iahs2022-704, 2022.

For demographic, societal and climatic reasons, many countries have to manage changing agricultural territories and the evolution of these agricultural territories should accelerate by the global changes. In the Mediterranean area, traditional gravity-fed irrigation systems and associated channel networks are still widely used in agricultural territories. These systems affect landscapes and have had a lasting effect on the water cycle. Gravity-fed irrigation water contributes to the creation or maintenance of wetlands and contributes to the recharge of aquifers. A specific biodiversity is observed in irrigated areas and in areas crossed by irrigation canal networks. On the outskirts of urban centers, urbanization often extends over agricultural land, leading to an abandonment of gravity irrigation. In a climate change context, gravity irrigation may also disappear in favour of other more water-efficient irrigation techniques.

The current challenges therefore relate to:

- the identification of solutions to ensure the sustainability of channel networks and to mitigate the impact of the disappearance of gravity-fed irrigation perimeters.

- the implementation of these solutions by land planners.

We focused our work on a business area created within a sector where water from channels formerly used for gravity-fed irrigation is now used for watering green areas via a pressure network. This choice makes it possible to perpetuate the network of canals carrying water over the territory but some services initially provided by the irrigated perimeters such as the groundwater recharge or the reception of a specific biodiversity are no longer guaranteed there.

The atypical management of a stormwater retention basin, combining stormwater and irrigation water, has led to the creation of an artificial wetland that encourages the establishment of aquatic-dependent vertebrate animal species, including the unexpected presence of typical reed bed species. On the other hand, the invertebrate population remains sparse due to the rather irregular watering rate of the wetland.

Monitoring of water levels in this wetland shows that this basin leads to very large exchanges of water, both to groundwater and to the atmosphere, which can compensate for the flows disturbance induced by the abandonment of gravity irrigation.