Temporary storage areas (TSAs) are a nature-based solution for attenuating flood peaks through the temporary detention of floodwaters in small (up to 10,000 m3) storage ponds on hillslopes or floodplains. Despite their increasing prevalence as part of Natural Flood Management (NFM) schemes in the UK, empirical evidence demonstrating their capability to mitigate flooding at catchment scales is limited. Addressing this evidence gap is a key priority for informing future flood risk management policies.In this study, we intensively monitored a prominent NFM scheme in the Littlestock Brook, a lowland rural sub-catchment (6.4 km2) of the River Evenlode in England. Ten TSAs providing a combined 25,000 m3 of flood storage were implemented between 2018 and 2020 to protect a flood-prone settlement. Measurements of river discharge (5 min), TSA stored volume (5 min), and precipitation (10 min) enabled the filling and drainage dynamics of individual TSAs to be quantified. The monitoring period (2019-2021) captured several notable storm events, including one with an estimated return period of 1 in 37 years. To quantify the aggregated impact of multiple TSAs on flood hydrographs at the catchment scale, observed TSA inflows and river discharge were used within a time-of-travel based hydrograph reconstruction approach to enable the estimation of downstream discharge in the absence of TSAs. Comparison of observed (with TSAs) and reconstructed (without TSAs) hydrographs indicate a 23% reduction in peak discharge for a 1 in 16-year return period storm. Furthermore, analysis of individual TSAs revealed substantial variation in storage utilisation and drainage during and after storms. These results provide quantitative evidence of how TSAs function both individually and in combination. The potential effectiveness of TSAs as a sustainable Natural Flood Management intervention will be discussed.

Hydrologic observatories have been a cornerstone of hydrologic science for many decades, advancing hydrologic process understanding with focused field observations and targeted experiments. Observatories present our key opportunity for achieving great depth of hydrologic investigation, most often at the headwater catchment scale. We address two main aspects concerning hydrologic observatories in this contribution: (1) While reviews of individual hydrologic observatories and observatory networks exist, no study has investigated the diversity of observatories to understand whether common aspects increase the likelihood of scientific success. We synthesise information from 80 hydrologic observatories and conduct 25 interviews with observatory leads to fill this gap. We find that scientific outcomes are most enhanced by involving scientific and stakeholder communities throughout observatory inception, design, and operation; by enabling infrastructure to be adjustable to changing ideas and conditions; and by facilitating widespread data use for analysis. (2) While observatories are key for advancing local hypotheses, the transferability of knowledge gained locally to other places or scales has often been difficult or even remained elusive. Headwater catchments in particular show a wide range of process controls often only understood if viewed in a wider regional context of climatic, topographic, or other gradients. We therefore must place observatories into the wider tapestry of hydrologic variability, for example through comparison with large samples of catchments, even though significantly less information is available to characterise these diverse systems. We provide some thoughts on how this connection could be improved through digital infrastructure, mobile observational infrastructure and a renewed focus on gradients and contrasts of controlling processes. We believe that there is a significant opportunity to enhance transferrable knowledge creation in hydrology.

Observational data on soil physical and hydraulic properties are important for improving our understanding of hydrological processes. This is particularly relevant given current interest in the potential of land-based "natural flood management" measures (and related concepts: "nature-based solutions" and "working with natural processes") to reduce flood risk. Therefore, a detailed survey of seven field sites under different land uses and management practices in the Thames catchment, UK, was undertaken as part of the LANDWISE project. Measurements (n = 1300) included soil surface infiltration rate, saturated hydraulic conductivity, bulk density, estimated porosity, soil moisture, and soil moisture retention. Field sites comprised three arable fields on shallow soils over limestone, two arable fields on free-draining loamy soils over chalk, and permanent grassland and broadleaf woodland on slowly permeable soil over mudstone. Soil sampling points covered infield areas, trafficked areas (e.g. tramlines), and untrafficked margins. Samples were generally taken at five depths ranging from the soil surface to 100 cm below ground level. Soil saturated hydraulic conductivity measurements were made at 25 and 45 cm depths. Soil samples and measurements were taken between April and October 2021, with repeats taken pre- and post-harvest (arable sites). These data provide valuable insight into the hydrological behaviour of soils under contrasting management, including both conventional and innovative agricultural practices (e.g. herbal leys, mob grazing, and controlled traffic). Dataset applications include improving the performance of hydrological and land surface models and validation of remotely sensed soil observations. The dataset is publicly available at 10.5285/a32f775b-34dd-4f31-aafa-f88450eb7a90 (Trill et al., 2022).

Climate extremes like floods and droughts pose significant threats to both human communities and natural landscapes. The EU Horizon SpongeScapes and SpongeWorks projects aim to enhance landscape resilience against these hydrometeorological extremes by exploring "landscape sponge functions" – the natural ability of landscapes to absorb, store, and gradually release water. The SpongeScapes project investigates various nature-based solutions (NBS) across diverse European sites with varying climates, geographies, and soil conditions, to address three main questions: (i) what is the longer-term effectiveness of sponge measures (and what indicators/metrics are more adequate); (ii) what is the overall effect of all sponge measures in a catchment (i.e. sponge strategies); (iii) what are the main co-benefits and tradeoffs of sponge measures and strategies. Here we will present a framework of context-specific 'Sponginess' indicators and metrics, in particular to assess the sponge function of water retention capacity in fluvial and agricultural sponge measures and strategies (catchment-wide combination of measures), with applications to SpongeScapes UK sites in the river Thames basin where work has been done since 2017 and is ongoing. These sites include the Littlestock brook, a headwater catchment in an agricultural landscape where a diversity of nature-based solutions (woody leaky dams, field corner bunds, wet woodland planting) have been implemented, as well as several farms where regenerative agricultural practices (RAPs) have been followed to improve soils, surface and ground water management. Results on applying our sponge indicators framework will be presented and discussed based on ongoing field investigations, including analyses based on novel low-cost telemetered water level data in the fluvial site, as well as survey data for soil bulk density, water retention functions, infiltration and hydraulic conductivity for the agricultural fields.

Implementing Nature-based solutions (Nbs) can potentially reduce the flood risk in catchments and improve water and soil quality and biodiversity. Understanding the hydrological functioning of the Nbs interventions is important in determining their effectiveness in reducing flood risks. This study reports the findings from two UK projects namely the Littlestock Brook Natural Flood Management (NFM) pilot and LANDWISE (Land Management in Lowland Catchments for Integrated Flood Risk Reduction). The Littlestock Brook NFM study showed that the Nbs interventions successfully attenuated all storm event discharge peaks during the monitoring period (up to 55% reductions) and that over 40% of the total storage volume remained available throughout all events. The LANDWISE project demonstrated that whilst increased organic matter improves soil structure and porosity, innovative arable management practices (e.g., controlled traffic and min till) can also improve soil structure and porosity, increasing soil hydraulic conductivity and therefore NFM potential.

Tryptophan-like fluorescence (TLF) is used to indicate anthropogenic inputs of dissolved organic matter (DOM), typically from wastewater, in rivers. We hypothesised that other sources of DOM, such as groundwater and planktonic microbial biomass can also be important drivers of riverine TLF dynamics. We sampled 19 contrasting sites of the River Thames, UK, and its tributaries. Multivariate mixed linear models were developed for each site using 15 months of weekly water quality observations and with predictor variables selected according to the statistical significance of their linear relationship with TLF following a stepwise procedure. The variables considered for inclusion in the models were potassium (wastewater indicator), nitrate (groundwater indicator), chlorophyll-a (phytoplankton biomass), and Total bacterial Cells Counts (TCC) by flow cytometry. The wastewater indicator was included in the model of TLF at 89 % of sites. Groundwater was included in 53 % of models, particularly those with higher baseflow indices (0.50-0.86). At these sites, groundwater acted as a negative control on TLF, diluting other potential sources. Additionally, TCC was included positively in the models of six (32 %) sites. The models on the Thames itself using TCC were more rural sites with lower sewage inputs. Phytoplankton biomass (Chlorophyll -a) was only used in two (11 %) site models, despite the seasonal phyto- plankton blooms. It is also notable that, the wastewater indicator did not always have the strongest evidence for inclusion in the models. For example, there was stronger evidence for the inclusion of groundwater , TCC than wastewater in 32 % and 5 % of catchments, respectively. Our study underscores the complex interplay of wastewater, groundwater , planktonic microbes, driving riverine TLF dynamics, with their influence deter- mined by site characteristics.

<p>The river Thames catchment  passes through rural and urban centres covering many different environments and land uses. Therefore, it is exposed to a range of stresses from sewage pollution to run off from agriculture. As such, UKCEH has been conducting water quality monitoring of the Thames since 1997, which later expanded into the Thames Initiative. The Thames Initiative collects a wide range of chemical and biological data, at 19 sites across the Upper Thames Catchment and its tributaries. For 18 months, in 2012-13, fluorescence spectroscopy and PARAFAC analysis was used to identify 4 components of fluorescent organic matter (FOM). This research focusses on the role of the fourth component, C4, which represents a tryptophan like FOM(TLF). The study is looking at the peak’s temporal variability at all 19 sites within the Thames catchment, alongside nutrient and biological data. This will enable greater understanding TLF’s sources and pathways by analysing TLF’s interaction with other nutrients and pollutants.  There is robust research linking TLF to sewerage pollution and more widely anthropogenic activity. However, the understanding of TLF as a product of insitu production from microorganisms is still in relative infancy, particularly when looking for evidence in the field at a catchment level. In this study multiple variate linear modelling using forward stepwise regression techniques have been applied to the data at each site to investigate the sources of C4 across the catchment to understand both catchment and instream processes. The possible predictors available to each model were dissolved potassium (DK), total dissolved nitrogen (TDN), dissolved calcium (DCa), total bacterial counts(TBC) and chlorophyll <em>a</em>. The models used between 2-3 predictors (σ=2.53, μ =0.678). DK was the most common (18 models),  followed by TBC (11 models), then DCa and TDN (both 8 models) and finally chlorophyll <em>a</em> (2 Models). These results suggest a dominant source of C4 across the catchment is from the wastewater as dissolved potassium is a sewerage indicator.  Secondly the occurrence of TDN or dissolved  calcium suggest a more dominate baseflow path of the fluorescence at these sites, as found in previous analysis of these sites.  However, most novelty is the regular occurrence of TBC in the models. This suggests  the C4 component has a bacteriological element as well, which means it is likely there is an important contribution of TLF by insitu-production from microorganisms.</p>

The UK is planning to implement a £38M (€43M) Flood and Drought Research Infrastructure to facilitate the hydrological science and innovation needed to underpin the UK’s adaptation and resilience to floods and droughts. The UKRI’s intent to invest from its infrastructure fund was published following a ~2-year scoping study that determined research community requirements through reviews of comparable infrastructures across the UK, Europe and globally, community workshops and questionnaires, and direct engagement with potential beneficiaries from research, industry and government bodies. Significantly, the scoping study identified the importance of a digital infrastructure to enable a step-change in access to hydrological monitoring data. This would complement community access to the expected physical infrastructure for monitoring all phases of the water cycle across a range of catchment types.Key requirements for the proposed digital infrastructure, to be delivered through 2023-2028, include access to UK-wide hydrological data alongside new catchment observatory data, supporting field monitoring and innovation through open digital systems, advancing the state of the art for sensor data management, linking monitoring activities more closely with research data archives and delivering support for open science. The digital infrastructure would leverage technological developments e.g. in cloud-based virtual research environments, and be delivered alongside a significant community capacity building effort to support cultural change and enable researchers to transform ways-of-working to maximise its potential benefits.

Many countries fund catchment observatories and networks to provide observational data, test models and hypotheses, discover new insights, catalyse the development of new technologies and enhance interdisciplinary collaboration. These catchment networks provide a wealth of observational data, yet synthesising information across catchment observatories to produce process-based understanding is challenging. To generalise findings from place-based studies, we need greater synthesis across catchment networks and thus careful consideration of the design and topology of catchment observatories and monitoring networks.In this paper, we collate information from 80 catchment observatories/networks and conduct 21 questionnaires with project leads with the aim of reviewing the strengths and weaknesses of catchment observatories to provide recommendations that can inform future catchment observatory and network design. The catchment observatories encompass a wide range of flow regimes, science questions and spatial/temporal scales with 25, 33 and 22 observatories from the UK, Europe, and North America respectively. Most catchment observatories in the monitoring catalogue are concentrated in upland catchment systems monitoring flashy flow regimes, with very few focused on lowland systems and no catchment observatories focused on urban catchments. The choice of catchment observatory location was focused upon logistics and catchment characteristics, with logistics and the day-to-day running of the observatory highlighted as the aspect catchment observatory programme managers found most difficult. Many interviewees noted that the design of the observatory was a key phase in planning and an aspect they would have done differently.Finally, we recommend key design guidelines for future catchment observatory and networks. This includes the need for a scoping and planning phase, community co-designed, digital infrastructure that enables FAIR data provision, and flexible and extensible catchment topology. Critically, knowledge transfer needs to be built in from the beginning of catchment observatories to enable transferability of new insights and understanding across linked catchment networks to tackle grand challenges within hydrology.

In this paper, nature-based solutions (NBS) include: (1) natural flood management (NFM) interventions with a primary function of flood risk reduction but with additional multiple benefits for water quality improvements through the mitigation of diffuse pollution; and (2) ponds with a primary function of water quality improvement. This study assesses the ability of these NBS to trap pollutants in run-off within two small (3.4 km(2)) agricultural catchments (Upper Thames, UK). The masses of sediment, phosphorus, and organic carbon trapped by 14 features (since construction 2-3 years previously) were quantified through sediment surveying and sampling. Streamflow and suspended sediment monitoring downstream of features enabled catchment yields to be calculated. The features trapped a total of 83 t sediment, 122 kg phosphorus, and 4.3 t organic carbon. Although the footprint of the features was <1% of the catchment area, they drained 44% of the total land area and captured the equivalent of 15% of the total suspended sediment yield, 10% of the total phosphorus yield, and 8% of the particulate organic carbon yield as monitored at the catchment outlet over the monitoring period. Results reveal that accumulation rates were influenced by hydrological connectivity, with greater accumulation in features constructed directly on streams (online ponds), and those offline features that filled from overbank flows. The low to moderate accumulation rates observed in offline features suggests that their floodwater storage potential is only likely to significantly reduce in the medium term, necessitating maintenance after -10 years. Compared with topsoil in each contributing area, trapped sediment was enriched in phosphorus and carbon in the majority of features, having on average 50% higher phosphorus and 17% higher organic carbon concentrations than surrounding arable soils, highlighting its potential value for redistribution on farmland. Monitoring results demonstrate the potential of NBS, including NFM, to mitigate diffuse pollution in lowland catchments.

Here we present the UK vision for new world-leading hydrological observation networks and sensor innovation test beds that will provide the long-term datasets needed to enable the mitigation of the impacts of hydrological extremes. Plans are underway for a Floods and Droughts Research Infrastructure (FDRI). This represents a major capital investment expected to be funded by the UK Research and Innovation Infrastructure Fund and delivered through the Natural Environment Research Council (NERC) at an estimated cost of £38m. FDRI is urgently needed to make the UK more adaptable and resilient to floods and droughts. It will include major new hydrological catchment instrumentation, with innovative technology to provide observations of key components of the terrestrial water cycle, and in-field facilities for trialling and developing new sensing technologies. Extensive community consultation and reviews have identified key science questions that are being used to inform infrastructure design. Successful impact will be enabled through strong investment in digital infrastructure to achieve a hydrological data commons. Integrated near real-time datasets will be publicly accessible, consolidated and inter-operable, ready for application specific analysis and modelling. As FDRI planning develops, there are opportunities to design-in the latest thinking on catchment monitoring strategies with innovative sensing, and to ensure that long-term hydrological datasets will be able to answer a wide variety of future research questions.

Natural Flood Management (NFM) is a nature-based solution for reducing flood risk whilst delivering multiple benefits such as water quality improvements through the mitigation of diffuse pollution (e.g. from soil erosion). This study aimed to assess the ability of NFM storage features to trap potential pollutants in run-off from two small (3.4 km2) agricultural catchments. The masses of sediment, total phosphorus and organic carbon trapped by 14 NFM features (since construction 2 to 3 years previously) were quantified through sediment surveying and sampling. Streamflow and suspended sediment monitoring downstream of the features enabled catchment fluxes to be calculated. The features trapped a total of 83 tonnes sediment, 122 kg phosphorus, and 4.3 tonnes organic carbon over 2 to 3 years of functioning. Although the footprint of the features was <1% of the catchment area, they drained 44% of the total land area and were able to capture the equivalent of 25% of the total suspended sediment flux (22% of the fine (silt and clay) sediment flux), 14% of the total phosphorus flux, and 13% of the particulate organic carbon flux during the monitored period. Results show how accumulation rates were influenced by hydrological connectivity, with greater accumulation in features constructed directly on streams (online features), and offline features which filled from streamflow diverted by instream woody dams. Compared with the topsoil in each contributing area, trapped sediment was enriched in phosphorus and carbon in the majority of features, having on average 50% higher phosphorus and 17% higher organic carbon concentrations than surrounding arable soils, highlighting its potential value for redistribution on farmland. The results of this monitoring demonstrate the potential of NFM interventions to provide additional value by mitigating diffuse pollution in lowland catchments.

High-resolution monitoring of water quality and ecosystem functioning over large spatial scales in expansive lowland river catchments is challenging. Therefore, we need modeling tools to predict these processes at locations where observations are absent. Here, we present a new approach to estimate ecosystem metabolism underpinned by a high-resolution, process-based model of in-stream flows and water quality. The model overcomes the current challenges in metabolism modeling by accounting for oxygen transport under varying flows and oxygen transformations due to biogeochemical processes. We implement the model in a 62-km-long stretch of the River Thames, England, using observations spanning 2 yr. Model outputs suggest that the river is primarily autotrophic from mid-spring to mid-summer due to high biomass during low-flow periods, and is heterotrophic during the rest of the year. Ecosystem respiration in upstream reaches is driven mainly by biochemical oxygen demand, autotrophic respiration, and nitrification processes, whereas downstream sites also show a control of benthic oxygen demand in addition to the aforementioned processes. Using empirical modeling, we analyze the sensitivity of our estimated metabolism rates to multiple environmental stressors. Results demonstrate that empirical models could be useful for rapid river health assessments, but need improvements to reproduce peak metabolism rates. The process-based model, although more complex than existing in situ approaches to metabolism quantification, allows inference when gaps in continuous observations are present. The model offers additional benefits for predicting metabolism rates under future scenarios of environmental change incorporating multiple stressor effects.

Catchment-based approaches that work with natural processes for fluvial flood risk reduction are currently the subject of much interest both internationally and in the UK, where they are known as Natural Flood Management (NFM). NFM schemes typically seek to replicate, restore, or enhance natural features of the environment so as to store and/or slow floodwaters during storm events. Benefits over traditional hard-engineered flood management approaches include reduced capital costs and carbon emissions, and they can deliver positive outcomes for both water quality and biodiversity. Despite a small number of studies indicating their potential value, the further uptake of NFM schemes is limited by a lack of empirical evidence demonstrating their effectiveness.We present results from an intensive monitoring network within a tributary (catchment area 3.4 km2) of the Littlestock Brook, a lowland agricultural catchment within South East England that presents a flood risk to the downstream village of Milton-under-Wychwood. The catchment forms part of the first NFM scheme of its kind within the River Thames basin, currently being delivered in partnership by the Evenlode Catchment Partnership and the Environment Agency as part of a five-year project (2016-2021). Precipitation, stream discharge, and water level within eight offline storage areas have been continuously monitored since September 2019. High resolution topographic surveys of each storage area enable filling, storing, and drainage dynamics to be determined and compared with downstream hydrograph metrics. A series of storm events between October 2019 and February 2020 have provided a unique dataset for investigating the performance of the NFM scheme.Data from four storms with estimated peak-discharge return periods ranging from 2.7 to 5.5 years demonstrate the potential for reducing peak discharge. During the largest storm, flood volume across the peak of the hydrograph was reduced by 22%, with 64% of total storage capacity remaining unused. Variations in the filling, storing, and drainage characteristics of each storage area have consequences for the overall effectiveness for reducing downstream flood risk and these will be discussed.

Agri-environmental management has been promoted as an approach to enhance delivery of multiple ecosystem services. Most agri-environment agreements include several actions that the farmer agrees to put in place. But, most studies have only considered how individual agri-environmental actions affect particular ecosystem services. Thus, there is little understanding of how the range of agri-environmental actions available to a farmer might be deployed on any individual farm to enhance multiple services. To address this knowledge gap, we carried out an experimental study in which we deployed a set of agri-environmental actions on a commercial farm in southern England. Agri-environmental actions comprised wildflower margins and fallow areas in arable fields, creating and enhancing grassland with wildflowers, and digging ponds. Alongside biodiversity responses, we measured effects on a number of ecosystem services: pollination, pest control, crop and forage yield, water quality, climate regulation and cultural services. Wildflower margins enhanced invertebrates, pest control and crop yield, and aesthetic appeal. A greater number of pollinators was linked to enhanced oilseed rape yield. But these margins and the fallows did not prevent run-off of nutrients and sediment into waterways, and showed limited carbon sequestration or reduction of greenhouse gas emissions. Newly-dug ponds captured large amounts of sediment and provided aesthetic appeal. Grasslands had higher soil carbon content and microbial biomass, lower N20 emissions, and net sequestration of carbon compared to arable land. Enhancement of grassland plant diversity increased forage quality and aesthetic appeal. Visitors and residents valued a range of agri-environmental features and biodiversity across the farm. Our findings suggest one cannot necessarily expect any particular agri-environmental action will enhance all of a hoped-for set of ecosystem services in any particular setting. A bet-hedging strategy would be for farmers to apply a suite of options to deliver a range of ecosystem service benefits, rather than assuming that one or two options will work as catch-all solutions.

There is a no lack of significant open questions in the field of hydrology. How will hydrological connectivity between freshwater bodies be altered by future human alterations to the hydrological cycle? Where does water go when it rains? Or what is the future space–time variability of flood and drought events? However, the answers to these questions will vary with location due to the specific and often poorly understood local boundary conditions and system properties that control the functional behaviour of a catchment or any other hydrologic control volume. We suggest that an open, shared and evolving perceptual model of a region's hydrology is critical to tailor our science questions, as it would be for any other study domain from the plot to the continental scale. In this opinion piece, we begin to discuss the elements of and point out some knowledge gaps in the perceptual model of the terrestrial water cycle of Great Britain. We discuss six major knowledge gaps and propose four key ways to reduce them. While the specific knowledge gaps in our perceptual model do not necessarily transfer to other places, we believe that the development of such perceptual models should be at the core of the debate for all hydrologic communities, and we encourage others to have a similar debate for their hydrologic domain.

Agricultural land is a key source of fine sediment and nutrients, often contributing significantly to diffuse pollution and catchment water quality issues. In the UK, recent efforts to mitigate agricultural diffuse pollution and reverse declines in the chemical and ecological status of waterbodies have focussed on catchment-based approaches. These nature-based solutions involve restoring, enhancing, or emulating natural processes to slow, store, and filter water and contaminants as they move through a catchment. Several studies in UK catchments show the potential benefits of retention ponds and constructed wetlands, however their functioning has been shown to vary according to their design and the catchment typology they are situated within. To help further the evidence base on the effectiveness of ponds for mitigating diffuse agricultural pollution, we monitored a series of small, connected pond features (draining 0.3 km2 of slowly permeable clay soils) created as part of the Littlestock Brook Natural Flood Management (NFM) scheme. This lowland NFM scheme, situated in the headwaters of the River Thames basin (South East England), targets the issues of flooding and diffuse pollution, and is delivered through the Evenlode Catchment Partnership and Environment Agency as part of a five-year project (2016-2021). Water and sediment sampling were undertaken during both baseflows and stormflows to determine retention of sediment and phosphorus species within the ponds under varying hydrological conditions. Results demonstrate that during small to moderate storm events, the ponds were able to capture run-off and reduce peak concentrations of suspended solids and particulate phosphorus. However, during large magnitude events, the ponds became inundated and resuspension of previously deposited sediment caused a net loss of material from the system. We estimate that the annual settling flux within the pond series is 16.48 tonnes (±5.77) for sediment, and ~0.014 tonnes for phosphorus. This equates to 17% (±6) of the annual suspended sediment load for the wider 3.4 km2 sub-catchment area. This study highlights the complexities of sediment dynamics in connected pond features and the importance of maintenance for retention efficiency.

The creation of ponds and wetlands has the potential to alleviate stream water quality impairment in catchments affected by diffuse agricultural pollution. Understanding the hydrological and biogeochemical functioning of these features is important in determining their effectiveness at mitigating pollution. This study investigated sediment and nutrient retention in three connected (on-line) ponds on a lowland headwater stream by sampling inflowing and outflowing concentrations during base and storm flows. Sediment trapping devices were used to quantify sediment and phosphorus accumulations within ponds over approximately monthly periods. The organic matter content and particle size composition of accumulated sediment were also measured. The ponds retained dissolved nitrate, soluble reactive phosphorus and suspended solids during baseflows. During small to moderate storm events, some ponds were able to reduce peak concentrations and loads of suspended solids and phosphorus; however, during large magnitude events, resuspension of deposited sediment resulted in net loss. Ponds filtered out larger particles most effectively. Between August 2019 and March 2020, the ponds accumulated 0.306 t ha−1 sediment from the 30 ha contributing area. During this period, total sediment accumulations in ponds were estimated to equal 7.6% of the suspended flux leaving the 340 ha catchment downstream. This study demonstrates the complexity of pollutant retention dynamics in on-line ponds and highlights how their effectiveness can be influenced by the timing and magnitude of events.

This annex considers some key ecosystem services associated with woodlands, including urban forestry in section 5. Many of the services provided by urban forests are considered in more detail elsewhere within this and other Annexes. Carbon sequestration and climate change mitigation potential of woodlands can be considered as regulating and maintenance ecosystem services and these are considered in Annex-3/ERAMMP Report-35: Future-proofing our Woodland. Biodiversity evidence is detailed in Annex-1/ERAMMP Report-33: Biodiversity. Landscape services are covered under the cultural ecosystem services section - RDS wrote this.