Fast-growing plantations have been expanding in Brazil in the last 50 years, increasing productivity by over 40 m3 / ha in reduced cycles between 5 and 15 years. In the 1990s, environmental warnings about these plantations guided research projects seeking to understand their effects on water and propose forest management actions to minimize them. The assessment of forest management effects on water resources is conducted by long-term experiments in paired catchments. In this study, we present some studies conducted at the hydrological monitoring center of Itatinga Experimental Station, of the University of São Paulo, where hydrological monitoring began in 1987, and currently conduct 4 catchments under different forest management regimes: fast-growing industrial management, long-term forest mosaic management, native forest restoration and long-term coppiced management. Results show that in a site with deep soils and good natural water regulation, main hydrological effects still occur when forest management intensifies, increasing water consumption and making the flow regime vulnerable to intra- and inter-annual seasonality. Regarding water quality, weekly sampling showed little interference of forest management on water chemistry; besides, more intensive management increased the concentration of nutrients in the water. There were no differences in water use in Eucalyptus plantations aged between 10 and 17 years and the use of coppice management had in the first 2 years higher water use than new plantations. The different types of management adopted directly affected the amount of water used, showing that high water demand forest plantations at water deficit regions, water availability is directly controlled by the forest management regime.

Hydrological analyses and their associated uncertainties are a function of their supporting observational datasets. Publicly available large-sample hydrology datasets covering a range of climates, times, and locations can be used to support inter-watershed comparisons, pattern identification, and watershed regionalization studies. However, most of the large-sample datasets are limited to a series of basic measurements such as precipitation, air temperature, and streamflow. Here we synthesized data from 30 intensively monitored catchments with soil moisture, snowmelt, and other hydrometeorological observations at daily scale across the US. This data synthesis product, CHOSEN (CONUS/Comprehensive Hydrologic Observatory SEnsor Network), includes watersheds from the Long-Term Ecological Research (LTER) and Critical Zone Observatory (CZO) networks, and several other ecological and hydrological observatories. Catchments span diverse climate gradients and encompass multiple biomes and ecosystems. To achieve a consistent and standardized data product, we first implemented data cleaning and control procedures with strict variable naming conventions and unit conversions. Following data quality control, data processing methods, including gap filling by interpolation, linear regression, and climate catalog-based techniques, were implemented to produce alternative level-2 products. The data and metadata were written into self-describing NetCDF files, facilitating ease of access by multiple computer platforms. All python coding scripts, ranging from processing to accessing the NetCDF files, are publicly available, along with a user-friendly tutorial. The standardizations adopted here, and the availability of the data-processing pipeline, will facilitate future additions of new observations to this database. We anticipate that this synthesis will support comparative long-term hydrological studies and contribute to a growing body of open-source research in watershed and ecosystem science.

A. R. MacKenzie1,2,*, S. Krause1,2, K. M. Hart1, R. M. Thomas1,3, P. J. Blaen1,4, R.L. Hamilton1,2, G. Curioni1,2, S. E. Quick1,2, A. Kourmouli1,2, D. M. Hannah1,2, S. A. Comer-Warner1,2, N. Brekenfeld1,2, S. Ullah1,2 and M. C. Press1,51. Birmingham Institute of Forest Research, University of Birmingham, Birmingham B15 2TT, UK2. School of Geography, Earth and Environmental Science, University of Birmingham, Birmingham B15 2TT, UK3. Now at Big Sky Science Ltd, Sutton Coldfield, West Midlands, B72 1SY, UK4. Now at Yorkshire Water, Chadwick Street, Leeds, LS10 1LJ, UK5. Now at Manchester Metropolitan University, Manchester, M15 6BH, UK* Corresponding author:[email protected] moisture; stream metabolism; climate change; long-term monitoringSummary Paragraph The ecosystem services provided by forests modulate runoff generation processes, nutrient cycling and water and energy exchange between soils, vegetation and atmosphere. Increasing atmospheric CO2affects many linked aspects of forest and catchment function in ways we do not adequately understand. Most significantly, global levels of atmospheric CO2 will be around 40% higher in 2050 than current levels, yet estimates of how water and solute fluxes in forested catchments will respond to increased CO2 are highly uncertain. The Free Air Carbon Enrichment (FACE) facility of the University of Birmingham’s Institute of Forest Research (BIFoR) is an intensively monitored forest site specialising in fundamental studies of the response of whole ecosystem patches of mature, deciduous, temperate woodland to elevated CO2. Here, we introduce the facility, situated in a mixed land-use headwater catchment, with a particular focus on its environmental setting and the experimental infrastructure. The facility offers a significant opportunity to advance multi- and interdisciplinary understanding at the interfaces of soil, vegetation, hydrosphere and atmosphere under changed atmospheric composition.Site Description and MethodsThis summary complements online introductory videos (https://tinyurl.com/y3a2hkkx) and draws on the facility ‘White Book’, which is a live web-document containing extensive details of all the projects undertaken at the facility and details of instrument placement (heights, depths, spatial separation).The Wood Brook catchment and FACE facilityThe BIFoR FACE facility is situated in a mainly agricultural headwater catchment in the UK drained by the Wood Brook, and consists of the main elevated CO2 (eCO2) facility and a number of spatially nested satellite study sites including various forest plantations of different age and management (Figure 1). The facility is in lowland, rural, central England (52o48’ 3.6” N, 2o 18’ 0” W, 106 m above mean sea level (amsl)), within a patchy landscape typical of most temperate forest settings (Haddad et al., 2015). Wood Brook is a second-order stream with a 3.1 km² catchment ranging in elevation from 90 to 150 m amsl (Blaen et al., 2017) and subsequently draining into the River Severn catchment (the most voluminous river in England and Wales). The entire catchment is experiencing drastic land-use changes, having been converted to organic farming since 2019 and herbal lays in replacement of what was previously grass monoculture or arable, in addition to the new forest plantations.[Figure 1 here]The BIFoR FACE forest at the bottom of the Wood Brook catchment is a mature deciduous woodland, with dominant (25-m tall) English oak (Quercus robur ) planted around 1850. Sub-dominant (ca. 10 m tall) species consist of common hazel (Corylus avellana ), common hawthorn (Crataegus monogyna ), sycamore maple (Acer pseudoplatanus ) and other native species (Hart et al., 2019). Each stem with diameter-at-breast-height greater than 10 cm has been geolocated and tagged. Centimetre-scale forest structure was measured by a lidar overflight in August 2014 and by terrestrial laser scanning (private communication, Eric Casella, Forest Research, Surrey, UK); this structure establishes the basis for penetration of air, light, and water into the forest canopy.The central, eCO2 component of BIFoR FACE consists of nine experimental patches of 15 m radius (Hart et al., 2019). Three ‘undisturbed’ (or ‘ghost’) patches have no CO2-dosing infrastructure; three ‘control’ patches are exposed to ambient CO2 concentrations delivered via the same infrastructure used in the three ‘treatment’ patches to maintain +150 ppmv above ambient CO2 at all levels of the canopy. Elevated CO2 is maintained during daylight hours from oak bud burst (ca. 1st April) to last leaf fall (ca. 31st October). The CO2-dosing system works well; one-minute running means are within 15% of target in the treatment plots, with less than 1% of the time showing deviation above 10% of the baseline value in the control plots (Hart et al., 2019). The first season with eCO2 was 2017 and the treatment will continue until at least 2026. A parallel study of the effect of nitrogen and phosphorus addition began in 2020 in the forest away from the FACE patches.Surrounding the BIFoR FACE, the Wood Brook catchment hosts several long-term forest hydrological observatories. In partnership with the estate owners, young mixed-deciduous plantations are subjected to different manipulation treatment including irrigation and fertilisation experiments.The environmental contextThe climate at the Wood Brook catchment is that of the temperate maritime zone of north-west Europe (Barry and Chorley, 2010). The site-mean annual temperature (MAT) measured between 2016 and 2019 was 10.6 ± 0.8 oC and its mean annual precipitation (MAP) was 676 ± 66 mm. This situates BIFoR FACE well inside the MAT-MAP climate space for temperate forests (Sommerfeld et al., 2018). The catchment is within the area covered by the Central England Temperature record, which provides a time series back to 1772 (Parker et al., 1992).The Wood Brook catchment is situated in a Nitrate Vulnerable Zone (European Union Directive 91/676/EEC) with mean nitrate concentrations in the Wood Brook ranging from 5 to 7 mg N l-1 (Blaen et al., 2017). The contemporary reactive nitrogen deposition from the atmosphere in the catchment is ~22 kg N ha-1 y-1 with an ammonium to nitrate deposition ratio of 7:3 (private communication, S. Tomlinson, UK Centre for Ecology & Hydrology). Deposition of this scale represents less than about 15% of the total nitrogen nutrition of temperate deciduous forest trees (Rennenberg and Dannenmann, 2015).Site infrastructureThe Wood Brook is equipped with two continuous water quality monitoring stations comprising in-stream sensors measuring stage, water temperature, and electrical conductivity continuously (up to every 10 seconds). Sensors to measure further parameters (UV-VIS absorbance, DO, pH, and turbidity) are housed in an insulated kiosk located on the streambank (Blaen et al., 2017a). An ISCO peristaltic pump (Lincoln, NE, USA) passes 1 L of stream water through these sensors every hour. Continuous stream monitoring is supplemented with campaign-based sampling facilitated by networks of surface water ISCO autosamplers, for instance during tracer tests (Blaen et al., 2017a,b), as well as spatially nested multi-level mini-piezometers installed in the streambed to investigate streambed biogeochemical processes and groundwater-surface water interactions (Comer-Warner et al., 2019, Comer-Warner et al., 2020).Soil moisture in the main BIFoR FACE facility is monitored by 12 cm long frequency domain sensors (CS655 by Campbell Scientific, claimed accuracy ± 3 % v/v for ‘typical’ soils) installed diagonally from the surface in groups of three spaced 1 m apart, with two groups in the ’control’ and ’treatment’ patches and one group in the ’ghost’ patches, and monitoring at 15 to 30 min resolution.In addition, one of the juvenile plantations close to the catchment outlet has been instrumented since 2016 with active fibre-optic distributed temperature sensing (FO-DTS) for measuring soil temperature and soil moisture at a submeter spatial resolution, resulting in 1850 soil temperature and soil moisture sampling locations across the site, ranging from 10-40 cm depths (Ciocca et al., 2020). The retrieval from the FO-DTS has a maximum at 38%v/v, a value empirically determined from a soil-specific field calibration against point soil moisture sensors installed adjacent to the fibre-optic cable. The variability shown for the FO-DTS is that for 4 quasi-independent measurements per day at 25 cm intervals along the fibre-optic cable. Uncertainties of ca. 3-5% v/v have been reported for soil moisture measurements with the DTS technique (Gamage et al. 2018).Each treatment (eCO2) and control experimental patch is ringed by 16 free‐standing, climbable, lattice towers that reach 2-3 m above the local oak canopy; a 17th tower is sited in the centre of each patch. The lattice towers are secured by screw piles; the experimental site contains no concrete foundations or guy wires. Access to the experimental patches is via low-level walkways raised approximately 30 cm above ground level to prevent compaction. Canopy access above 5 m is contracted to climbing arborists or achieved using a bespoke canopy access system (CAS) installed from the 17th central tower of each infrastructure array. The CAS is operated by trained staff so that rope access training is not required for researchers. Welfare and simple laboratory facilities are provided. Elevated CO2 dosing, canopy access, and routine monitoring is operated by a team of six technical staff permanently stationed at BIFoR FACE.Four meteorological masts are located at the periphery of the woodland and a 40 m ‘flux tower’ stands towards the downwind end of the wooded area so that its flux ‘footprint’ is within the forest for the prevailing south-westerly winds. During dosing, true biogeochemical CO2 fluxes are, of course, obscured by the gas released to provide the eCO2 treatment effect but sensible and latent heat fluxes are recorded.Figure 2 illustrates the flow of data and tissue samples into their permanent repositories. Other equipment (not shown) is deployed ad hoc within specific projects.[Figure 2 here.]To complement the experimental infrastructure in the Wood Brook catchment and BIFoR FACE facility, an integrated groundwater-surface water model has been developed and validated by a combination of flow signatures and applied to investigate stream and subsurface water and energy balance in response to forest shading (Qiu et al., 2019).Example ResultsSoil moisture dynamics, stream discharge, and water quality in mature forest and young plantationExample core data (precipitation and FACE soil water content, discharge and DO) and project-specific data (field-scale soil moisture measured by FO-DTS at 10 cm) demonstrate the value of long-term integrated monitoring in ecohydrological observatories such as the Wood Brook catchment (Figure 3).The variability of the temperate maritime climate is evident: prolonged wetting and drying events with occasional, shorter, high-intensity rainfall events. Signals can take a long time to emerge within such variability, which is a key argument for a long-term experimental platform such as BIFoR FACE. The time series at this relatively early stage suggests that: (i) the plantation is systematically wetter than the neighbouring FACE forest even though the plantation slopes downwards towards FACE; (ii) there is significant spatial variability in the plantation and FACE forest; and (iii) the eCO2 patches are drier than the aCO2 and undisturbed patches. Point (iii) is a result of spatial variability in the forest; the strength of soil moistening due to eCO2, if any is present (cf. Ellsworth, 1999; Drake et al., 2016), remains to be quantified.Corresponding water levels at the Wood Brook catchment outlet highlight the general “flashiness” of the flow regime with relatively fast responses to precipitation events for a permeable catchment as well as fast recession of flow (Figure 3 bottom). This example time series of one of our monitoring stations also indicates some of the challenges in maintaining consistent quality control throughout long-term observation networks. In addition to data losses induced by power supply failures in Spring 2019, observed values up to early 2019 were an order of magnitude lower than from summer 2019 onwards due to repeated sedimentation of the water level sensor and recurring changes to the channel cross sectional profile that finally led to a relocation of the sensor as indicated in Figure 3. The additional value of continuously monitored water level and water quality data (as highlighted by the example of dissolved oxygen in Fig 3 bottom) extends beyond the ability to observe long-term trends in catchment behaviour in response to land-use changes but also provides opportunity to enhance mechanistic process understanding of in stream metabolism and biogeochemical processing as well as event-based activation of pollution sources (Blaen et al., 2017a).[Figure 3 here.]Data protocol and availabilityAll projects form part of the overall collaborative effort to understand catchment behaviour and forest form and function, and all facility users sign a data protocol to that effect. The BIFoR FACE science community believe and advocate transparency in science, assured through open data after an agreed period of privileged use.The facility is supported by a full-time data manager (author GC), responsible for tracking all data and tissue samples. The data is available upon request; an open data repository for a subset of core data is under construction.The continuous streams of data are handled by a suite of dataloggers and a local LAN network which allows data to be saved on the BIFoR FACE facility server (Figure 2). A back-up server located on site in a separate building stores a daily image of the primary server. Data is transferred daily to the University of Birmingham servers and the raw and processed data (i.e. organised in a consistent format and cleared of evident issues) are stored separately to improve resilience. Non-continuous data collected by researchers is stored in the University of Birmingham servers and handled directly between researchers and the data manager.All tissue is recorded when sampled and a chain-of-custody initiated using Pro-curo. Quenching of biological samples to -70oC is accomplished on-site using a dry shipper (BioTrex-10, Statebourne Cryogenics, Tyne & Wear, UK), avoiding the need for transporting liquid nitrogen. Short-term tissue storage at 5oC and -20 oC can be accommodated on-site, but the permanent tissue bank resides at the University of Birmingham Edgbaston campus.In summary, BIFoR FACE is an ambitious field facility designed primarily to measure the whole-system response of mature temperate forest to elevated CO2, but suitable for a wide range of complementary catchment studies. The facility is highly collaborative in nature and welcomes partners11https://www.birmingham.ac.uk/research/bifor/get-involved/index.aspx who wish to contribute as part of a multidisciplinary Community of Practice.AcknowledgmentsWe very gratefully acknowledge support from the JABBS Trust, Norbury Park Estate, The John Horseman Trust, Ecological Continuity Trust, NERC (grants NE/S015833/1, NE/P003486/1, NE/N020502/1; NE/T000449/1; NE/T012323/1), and the University of Birmingham. The soil moisture FO-DTS system installation was led by Francesco Ciocca while holding joint positions at the University of Birmingham and at Silixa Ltd. (London, UK).The BIFoR FACE facility cannot run without the dedicated support of its operations team (currently; Nicholas Harper, Peter Miles, Thomas Downes, Gael Denny and Robert Grzesik, formerly; Gary McClean and Anna Gardner). Foundational contributions to the design and implementation of the facility were made by Michael Tausz and Sabine Tausz-Posch. The FACE facility eCO2 treatment uses the system designed by John Nagy and installed by Keith Lewin, both of Brookhaven National Lab, USA. We acknowledge the considerable scientific input of visiting fellows (David Ellsworth, Kristine Crous, Debbie Hemming, Rich Norby, Theresa Blume and Mantha Phanikumar) and former researchers (Will Allwood, Alex Poynter, Elizabeth Hamilton). We gratefully acknowledge strategic guidance from BIFoR Directors (Rob Jackson, Jerry Pritchard, and Nicola Spence) and the Science Committee (Christine Foyer, Vincent Gauci, Francis Pope, and Estrella Luna Diez).ReferencesBarry, R. G., and Chorley, R. J. (2010) Atmosphere, Weather and Climate, 9th ed., Routledge, London.Blaen, P., K. Khamis, C. Lloyd, S. Comer-Warner, F. Ciocca, R. M. Thomas, A. R. MacKenzie, Stefan Krause (2017a), High-frequency monitoring of catchment nutrient exports reveals highly variable storm-event responses and dynamic source zone activation, J. Geophys. Res-Biogeosciences, 10.1002/2017JG003904Blaen P., Brekenfeld N., Comer-Warner S., Krause S. (2017b). Multitracer Field Fluorometry: Accounting for Temperature and Turbidity Variability during Stream Tracer Tests. Water Resources Research, 53,https://doi.org/10.1002/2017WR020815.Ciocca F., Abesser C., Findlay J., Chalari A., Mondanos M., Hannah D.M., Blaen P., Krause S. 2020. A Distributed Heat Pulse Sensor Network for Thermo-Hydraulic Monitoring of the Soil Subsurface. Quarterly Journal of Engineering Geology and Hydrogeology. 53. 352-365,https://doi.org/10.1144/qjegh2018-147Comer-Warner S., Ullah S., Kettridge N., Gooddy D., Krause S. (2019). Seasonal variability of sediment controls on carbon cycling in an agricultural stream. Science of the Total Environment. 688, 732-741,https://doi.org/10.1016/j.scitotenv.2019.06.317Comer-Warner, S.A., Gooddy, D.C., Ullah, S., Glover L., Kettridge N., Wrexler S.K., Kaiser J., Krause S. 2020. Seasonal variability of sediment controls of nitrogen cycling in an agricultural stream. Biogeochemistry. 148, 31–48 (2020). https://doi.org/10.1007/s10533-020-00644-zDrake, J.E., Macdonald, C.A., Tjoelker, M.G., Crous, K.Y., Gimeno, T.E., Singh, B.K., Reich, P.B., Anderson, I.C. and Ellsworth, D.S. (2016), Short‐term carbon cycling responses of a mature eucalypt woodland to gradual stepwise enrichment of atmospheric CO2concentration. Glob Change Biol, 22: 380-390. doi:10.1111/gcb.13109Ellsworth, D.S. (1999), CO2 enrichment in a maturing pine forest: are CO2 exchange and water status in the canopy affected?. Plant, Cell & Environment, 22: 461-472. doi:10.1046/j.1365-3040.1999.00433.xGalloway, J.N., Dentener, F.J., Capone, D.G. et al. (2004) Nitrogen Cycles: Past, Present, and Future. Biogeochemistry 70, 153–226. https://doi.org/10.1007/s10533-004-0370-0Gamage, D.N.V., Biswas, A., Strachan, I.B., Adamchuk, V.I. 2018. Soil Water Measurement Using Actively Heated Fiber Optics at Field Scale. Sensors 18 (4): 1116 DOI: 10.3390/s18041116Haddad, N.M., Brudvig, L.A., Clobert, J., Davies, K.F., Gonzalez, A., Holt, R.D., Lovejoy, T.E., Sexton, J.O., Austin, M.P., Collins, C.D., Cook, W.M., Damschen, E.I., Ewers, R.M., Foster, B.L., Jenkins, C.N., King, A.J., Laurance, W.F., Levey, D.J., Margules, C.R., Melbourne, B.A., Nicholls, A.O., Orrock, J.L., Song, D.X., Townshend, J.R., 2015. Habitat fragmentation and its lasting impact on Earth’s ecosystems. Sci. Adv. 1.https://doi.org/10.1126/sciadv.1500052Hart, Kris; Curioni, Giulio; Blaen, Philip; Thomas, Rick; Harper, Nicholas; Miles, Peter; Lewin, Keith; Nagy, John; Bannister, Edward; Cai, Xiaoming ; Krause, Stefan; Tausz, Michael; MacKenzie, A. Robert (2019) Characteristics of Free Air Carbon Dioxide Enrichment of a Northern Temperate Mature Forest. Glob Change Biol. doi:10.1111/gcb.14786Norby, R. J., M. G. De Kauwe, T. F. Domingues, R. A. Duursma, D. S. Ellsworth, D. S. Goll, D. M. Lapola, K. A. Luus, A. R. MacKenzie, B. E. Medlyn, R. Pavlick, A Rammig, B Smith, R Thomas, K Thonicke, A. P. Walker, Xiaojuan Yang, and Sönke Zaehle, Model-data synthesis for the next generation of forest FACE experiments, New Phytologist, 2015, DOI: 10.1111/nph.13593.Parker, D.E., T.P. Legg, and C.K. Folland. 1992. A new daily Central England Temperature Series, 1772-1991. Int. J. Clim., Vol 12, pp. 317-342.Payne, Richard John, Dise, Nancy B., Field, Christopher D et al. (3 more authors) (2017) Nitrogen deposition and plant biodiversity : past, present and future. Frontiers in Ecology and the Environment.https://doi.org/10.1002/fee.1528Qiu, H., Blaen, P., Comer‐Warner, S., Hannah, D. M., Krause, S., & Phanikumar, M. S. 2019. Evaluating a coupled phenology – surface energy balance model to understand stream – subsurface temperature dynamics in a mixed‐use farmland catchment. Water Resources Research, 55.https://doi.org/10.1029/2018WR023644Rennenberg, H., Dannenmann, M. (2015) Nitrogen nutrition of trees and temperate forests – the significance of nitrogen availability in pedosphere and atmosphere. Forests 6, 2820-2835.Sommerfeld, A., Senf, C., Buma, B. et al. (2018) Patterns and drivers of recent disturbances across the temperate forest biome. Nat Commun 9, 4355. https://doi.org/10.1038/s41467-018-06788-9Figure CaptionsFigure 1. (a) BIFoR FACE is located in Mill Haft (white dashed line; lighter patches show locations of the FACE arrays and control patches) in a patchwork of old-growth forest, new forest plantation on arable land, and arable fields. (b) Wood Brook catchment (white dashed line) with the stream running along the northern edge of Mill Haft. (c) Central England location of Mill Haft.Figure 2. A schematic view of the sensor deployment and tissue and data flow through BIFoR FACE and Wood Brook. The main experimental infrastructure elements are shown (left); replicates are indicated by “n = “. Data from electronic sensors are recorded in networked field dataloggers and relayed to the facility server. Back-up is carried out on-site and by daily data download to the main University of Birmingham servers with Retrospect software (Retrospect Inc. USA). Initial quality assurance is under the control of the BIFoR Data Manager (author GC) before data is released to the BIFoR FACE community. A parallel system operates for physical samples, the metadata from which enters the BIFoR FACE database via chain-of-custody software (Pro-curo Software Ltd, West Sussex, UK).Figure 3. a) time series of daily top-of-forest precipitation and soil moisture from distributed temperature sensing (DTS) by fibre-optic cable embedded at 10 cm depth between rows on new broadleaf forest plantation immediately south of the FACE forest (see Figure 1). b) Time series of shallow soil water content from an array of sensors in the FACE forest. The numbers of sensors at each part of the time series are reported in the top of the panel. c) Water level (in blue) and dissolved oxygen (in green) measured on the Wood Brook stream (see Figure 1).

The U.S. Department of Energy’s (DOE) East River community observatory (ER) in the Upper Colorado River Basin was established in 2015 as a representative mountainous, snow-dominated watershed to study hydrobiogeochemical responses to hydrological perturbations in headwater systems. Led by the Watershed Function Science Focus Area (SFA), the ER has both long-term and spatially-extensive observations paired with experimental campaigns. The Watershed Function SFA, led by Berkeley Laboratory, includes researchers from over 30 organizations who conduct cross-disciplinary process-based investigations and mechanistic modeling of watershed behavior in the ER. The data generated at the ER are extremely heterogeneous, and include hydrological, biogeochemical, climate, vegetation, geological, remote sensing, and model data that together comprise an unprecedented collection of data and value-added products within a mountainous watershed, across multiple spatiotemporal scales, compartments, and life zones. Within 5 years of data collection, these datasets have already revealed insights into numerous aspects of watershed function such as factors influencing snow accumulation and melt timing, water balance partitioning, and impacts of floodplain biogeochemistry and hillslope ecohydrology on riverine geochemical exports. Data generated by the SFA are managed and curated through its Data Management Framework. The SFA has an open data policy, and over sixty ER datasets are publicly available through relevant data repositories. A public interactive map of data collection sites run by the SFA is available to inform the broader community about SFA field activities. Here, we describe the ER and the SFA measurement network, present the public data collection generated by the SFA and partner institutions, and highlight the value of collecting multidisciplinary multiscale measurements in representative catchment observatories.

The Niwot Ridge and Green Lakes Valley (NWT) long-term ecological research (LTER) site collects environmental observations spanning both alpine and subalpine regimes. The first observations began in 1952 and have since expanded to nearly 300 available datasets over an area of 99 km2 within the north-central Colorado Rocky Mountains that include hydrological (n = 101), biological (n = 79), biogeochemical (n = 62), and geographical (n = 56) observations. The NWT LTER database is well suited to support hydrologic investigations that require long-term and interdisciplinary data sets. Experimentation and data collection at the NWT LTER are designed to characterize ecological responses of high-mountain environments to changes in climate, nutrients, and water availability. In addition to the continuation of the many legacy NWT datasets, expansion of the breadth and utility of the NWT LTER database is driven by new initiatives including (a) a catchment-scale sensor network of soil moisture, temperature, humidity, and snow-depth observations to understand hydrologic connectivity and (b) snow-albedo alteration experiments using black carbon to evaluate the effects of snow-disappearance on ecosystems. Together, these observational and experimental datasets provide a substantial foundation for hydrologic studies seeking to understand and predict changes to catchment and local-scale process interactions.

Improving our ability to detect changes in terrestrial and aquatic systems is a grand challenge in the environmental sciences. In a world experiencing increasingly rapid rates of climate change and ecosystem transformation, our ability to understand and predict how, when, where and why changes occur is essential for adapting and mitigating human behaviors. In this context, long-term field research infrastructures have a fundamentally important role to play. For northern boreal landscapes, the Krycklan Catchment Study (KCS) has supported monitoring and research aimed at revealing these changes since it was initiated in 1980. Early studies focused on forest regeneration and microclimatic conditions, nutrient balances and forest hydrology, which included monitoring climate variables, water balance components, and stream water chemistry. The research infrastructure has expanded over the years to encompass a 6790 ha catchment, which currently includes 10 gauged streams, ca. 1000 soil lysimeters, 150 groundwater wells, >500 permanent forest inventory plots, and a 150 meter tall tower (a combined ecosystem-atmosphere station; ICOS, Integrated Carbon Observation System) for measurements of atmospheric gas concentrations and biosphere-atmosphere exchanges of carbon, water, and energy. In addition to field infrastructures, the KCS has also been the focus of numerous high resolution multi-spectral LiDAR measurements. This large collection of equipment and data generation supports a range of disciplinary studies, but more importantly fosters multi-, trans-, and interdisciplinary research opportunities. The KCS attracts a broad collection of scientists, including biogeochemists, ecologists, foresters, geologists, hydrologists, limnologists, soil scientists and social scientists, and many others bringing their knowledge and experience to the site. The combination of long-term monitoring, shorter-term research projects, and large-scale experiments, including manipulations of climate and various forest management practices have contributed much to our understanding of the boreal landscapes functioning, while also supporting the development of models and guidelines for research, policy and management.

This study presents the results of a long-term paired catchment experiment in south central Chile (mean annual precipitation = 2,500 mm, 5% falling in summer, mean annual temperature = 10 °C) in which fast-growing plantations of exotic Eucalyptus spp. were clearcut and replaced with native temperate rainforest species as part of an ecological restoration project. Precipitation, streamflow, and vegetation were measured starting in 2006 in four small (3 to 5 ha) catchments with Eucalyptus globulus plantations and native riparian buffers in the Valdivian Coastal Reserve. In 2011, the 12-yr-old Eucalyptus plantations were harvested in three catchments, and the clearcut area was planted with native trees (Nothofagus dombeyi), and diverse native forest species regenerated vigorously. In the restoration period (2011 to 2019), annual streamflow increased in average by 21 – 73% compared to the 2006-2010 pre-treatment period, and as much as 100% in wet years and by more than 150% in fall and summer of some years. Streamflow was 50 to 100% lower than before treatment in two dry summers (2014-2015. Base flow increased by 28 to 87% during the restoration period (2011 to 2019) compared to the pre-treatment period, and remained elevated in later years despite low summer precipitation. Streamflow increases persisted through the first decade of restoration. Overall, these findings indicate that removal of Eucalyptus plantations immediately increased streamflow, and native forest restoration gradually restored deep soil moisture reservoirs that sustain base flow during dry periods, and these flows showed steady positive values in the last three years contributing to water provision ecosystem services. The results of this study are relevant to efforts to restore native forest ecosystems on land currently intensively managed fast-growing forest plantations. They also provide useful information to inform policy and decision-making related to options for climate change mitigation under a drying trend in South-central Chile. To our knowledge this study is the first to test streamflow response to native forest restoration in former fast-growing Eucalyptus forest plantations.

In this study, we introduce datasets that include both hydrological and meteorological records at the Nučice experimental catchment (0.53 km2) which is representative for an intensively farmed landscape in the Czech Republic. The Nučice experimental catchment was established in 2011 for the observation of rainfall-runoff processes, soil erosion processes, and water balance of a cultivated landscape. The average altitude is 401 m a.s.l., the mean land slope is 3.9%, and the climate is humid continental (mean annual temperature 7.9 °C, annual precipitation 630 mm). The catchment is drained by an artificially straightened stream and consists of three fields covering over 95 % of the area which are managed by two different farmers. The typical crops are winter wheat, rapeseed, and alfalfa. The installed equipment includes a standard meteorological station, several rain gauges distributed across the basin, and an H-flume that monitors stream discharge, water turbidity, and basic water quality indicators. Additionally, the groundwater level and soil water content at various depths near the stream are recorded. Recently, large-scale soil moisture monitoring efforts have been introduced with the installation of two cosmic-ray soil moisture sensors. The datasets consist of measured precipitation, air temperature, stream discharge, and soil moisture and are available online for public use. The cross seasonal, open access runoff generation datasets at this small-scale agricultural catchment will benefit not only hydrologists but also local farmers.

The present dataset is related to the Arc-Isère long-term environmental research part of the Rhône Basin Long Term Environmental Research Observatory. This alpine watershed located in the French Alps is characterized by high Suspended Particulate Matter (SPM) in very anthropogenized valleys. Suspended Sediment Concentrations (SSC) naturally observed in the river are very high, ranging from a few tens of milligrams per litre at low flow to tens of grams per litre during major natural hydrological events (floods, debris flows) or river dam hydraulic flushes. One research objective related to this site aims at better understanding the SSC dynamics along the river using a system of nested watersheds (Arvan, Arc, and Isère) in order to access to both temporal and spatial dynamics. Studies using this dataset are on the quantification of fine sediment fluxes but also on the related morphological changes due to fine sediment deposition or resuspension. Additionally, the observatory database can support studies on contaminants (either dissolved or particulate contaminant). Six hydro sedimentary stations monitor SSC with high frequency via turbidity sensors associated to automatic samplers. Discharge is measured via classical water level measurements and a rating curve. The oldest station (Grenoble-campus) started recording data from 2006 while others hydro-sedimentary stations were built from 2009 to 2011. Data are available in an online data website called “Base de Données des Observatoires en Hydrologie” (Hydrological observatory database, https://bdoh.irstea.fr/ARC-ISERE/) with DOI references for each site. The hydrological and sediment transport time series are stored, managed and made available to a wide community in order to be used at their full extent. This database is used as a data exchange tool for both scientists and operational end-users and as an online tool to compute integrated fluxes.

Headwater forest ecosystems of the western U.S. generate a large portion of the dissolved organic matter (DOM) transported across North America. Land cover changes that alter forest structure and forest species composition affect the quantity and composition of DOM transferred to aquatic ecosystems. Clear-cut harvesting effects ~1% of the forest area of North America annually, leaving most forests in varying stages of successional regrowth, and the total area of old-growth forest decreasing. The consequences of this widespread management practice on watershed carbon cycling remain unknown. We investigated the role of land cover change from old-growth subalpine forest to lodgepole pine dominated second-growth on the character and reactivity of DOM hillslope exports. We evaluated inputs of DOM from litter leachates and export of DOM collected at the base of trenched hillslopes during a three-year period (2016-2018) at the Fraser Experimental Forest in northcentral Colorado, USA. Dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) were higher in lateral subsurface flow draining old- versus secondary-growth forest. Fluorescence spectroscopy showed that the DOM exported from the old-growth forest was more heterogeneous and aromatic and that proteinaceous, microbially processed DOM components were more prevalent in the second-growth forest. Biological oxygen demand (BOD) assays revealed much lower microbial metabolism of both DOM inputs from litter leachate and subsurface exports from old-growth forest. Old-growth and second-growth forests are co-mingled in managed ecosystems, and our findings demonstrate that the influence of species composition on DOM inputs can affect the reactivity of DOM transferred from terrestrial to aquatic ecosystems.

Watershed description:The watershed is underlain by Oligocene tuffaceous and fossiliferous sandstone bedrock, rich in calcite, and clay-rich (Smectite) soils overlie a thick saprolite (Baille et al., 2007). BCI ranges in elevation from 26m asl to 167 m asl, is fully forested, with what has been characterized as a lowland seasonal tropical forest, with a mix of deciduous and evergreen trees. Annual rainfall averages 2,580 mm, with strong seasonality: the dry season is from December to May. BCI is one of the most intensively studied area of the global tropics because of the century-long presence of a research station and ongoing scientific investigation focused mainly on terrestrial forest ecology, entomology, animal behavior and related fields. The Lutz Creek data improve our understanding of basic hydrological processes and inform our ongoing research into the complex terrestrial ecosystems of the island and the region [bibliography below]. BCI is also home to the first of what is now a global network of more than 70 forest research plots known as the Forest Global Earth Observatory (ForestGEO, see https://forestgeo.si.edu/ ). ForestGEO is dedicated to advancing long-term study of the world’s forests to strengthen science capacity in an era of rapidly changing landscapes and climate to understand and predict forest dynamics

Beasley Lake Watershed is an agriculturally influenced drainage basin in western Mississippi that has been intensively studied for 25 years. As part of the USDA Conservation Effects Assessment Project (CEAP), the watershed has archived hydrology, precipitation, and water quality data in order to measure the effects of multiple USDA Natural Resources Conservation Service conservation practices on lake water quality. The long-term database is available to researchers using a web-based application, Sustaining the Earth’s Watersheds, Agricultural Research Data System (STEWARDS). STEWARDS is a GIS-based data retrieval application that encompasses spatial and temporal data collected from multiple sites within the watershed. This data note describes information located in the STEWARDS Beasley Lake Watershed database, including hydrology, precipitation, and water quality data. This information is valuable to researchers and agencies beyond the USDA as an available and useful database to improve the understanding of how land-use practices affect the water quality of shallow lake systems.

The 20 km² Galabre catchment belongs to the French network of critical zone observatories. It is representative of the sedimentary geology and meteorological forcing found in Mediterranean and mountainous areas. Due to the presence of highly erodible and sloping badlands of various lithologies, the site was instrumented in 2007 to understand the dynamics of suspended sediments (SS) in such areas. Two meteorological stations including measurements of air temperature, wind speed and direction, air moisture, rainfall intensity, raindrop size and velocity distribution are installed both in the upper and lower part of the catchment. At the catchment outlet, a gauging station records the water level, temperature and the turbidity (10 min. time-step). Water and sediment samples are collected automatically to estimate SS concentration-turbidity relationships, providing SS fluxes quantifications with known uncertainties. The sediment samples are further characterized by measuring their particle size distributions (PSD) and by applying a low-cost sediment fingerprinting approach using spectrocolorimetric tracers. Thus, the contributions of badlands on different lithologies to total SS flux are quantified at a high temporal resolution providing the opportunity to better analyze the links between meteorological forcing variability and watershed hydrosedimentary response. The set of measurements was extended to the dissolved phase in 2017. Both the river electrical conductivity and its major ion concentrations are measured each week and every three hours during storm events. This allows progress in understanding both the origin of the water during the events and the partitioning between particulate and dissolved fluxes in the critical zone.

The main objective of this study was to use an uncertainty version of a widely used monthly time step, semi-distributed model (the Pitman model) to explore the equifinalities in the way in which the main hydrological processes are simulated and any identifiable linkages with uncertainties in the available observational data. The study area is the Zambezi River basin and 18 gauged sub-basins have been included in the analyses. Unfortunately, it is not generally possible to quantify some of the observational uncertainties in such a data scarce area and mostly we are limited to identifying where these data are clearly deficient (i.e. erroneous or non-representative). The overall conclusion is that the equifinalities in the model are hugely dominant in terms of the uncertainties in the relative occurrence of different runoff generating processes, although water use uncertainties in the semi-arid parts of the basin can contribute to these uncertainties. The identification of landscape features that suggest the occurrence of saturation excess surface runoff provides some information to constrain the model. Improved independent estimates of groundwater recharge is also identified as a key source of observational data that would help a great deal in constraining the model parameter space and therefore reducing some of the model equifinality.

The Shenandoah Watershed Study (established in 1979) and the Virginia Trout Stream Sensitivity Study (established in 1987) serve to increase understanding of hydrological and biogeochemical changes in western Virginia mountain streams that occur in response to acidic deposition and other ecosystem stressors. The SWAS-VTSSS program has evolved over its 40+ year history to consist of a temporally robust and spatially stratified monitoring framework. Currently stream water is sampled bi-hourly during high-flow events at 3 sites and weekly at 4 sites within Shenandoah National Park (SHEN), and quarterly at 72 sites and on an approximately decadal frequency at ~ 450 sites within the wider western Virginia Appalachian region. Stream water is evaluated for pH, acid neutralizing capacity (ANC), base cations (calcium, magnesium, sodium and potassium ion), acid anions (sulfate, nitrate and chloride), silica and ammonium, with a subset of samples evaluated for monomeric aluminum and dissolved organic carbon. Hourly stream discharge (4 sites) and in-situ measurements of conductivity, water and air temperature (3 sites) are also measured within SHEN. Here we provide an overview and timeline of the SWAS-VTSSS stream water monitoring program, summarize the field and laboratory methods, describe the water chemistry and hydrologic data sets, and document major watershed disturbances that have occurred during the program history. Website links and instructions are provided to access the stream chemistry and time-series monitoring data in open-access federal databases. The purpose of this publication is to promote awareness of these unique, long-term data sets for wider use in catchment studies. The water chemistry and hydrologic data can be used to investigate a wide range of biogeochemical research questions and provide key inputs for models of these headwater stream ecosystems. SWAS-VTSSS is an ongoing program and quality assured data sets are uploaded to the databases annually.

Internal erosion is one of the most common causes of failure in hydraulic engineering structures, such as embankments and levees. It also plays a vital role in the geohazards (such as landslides and sinkhole developments) and more importantly, the earth landscape evolution, which has a broad environmental and ecosystem impacts. The groundwater seepage is multi-directional, and its multi-dimensional nature could affect the initiation and the progression of internal erosion. With a newly developed apparatus, we carry out nine internal erosion experiments under five different seepage directions. The results reveal that the critical hydraulic gradient increases as the seepage direction varies from the horizontal to the vertical. After a global erosion is triggered, preferential erosion paths distribute randomly from the bottom to the top of the specimen. If the seepage direction is not vertical, small preferential erosion paths merge into a large erosion corridor, in which the loss of fine particles is significant but negligible outside. Results of experiments manifest that the erosion is heterogeneous and three-dimensional, even in the unidirectional seepage flow. The particles are rapidly eroded at the early stage of the erosion, indicating a high erosion rate. With the erosion time increasing, the particle loss slows down and even ceases if the time is long enough. The erosion rate increases if the seepage direction approaches a vertical direction. Overall, the erosion rate approximately decreases with erosion time exponentially. We proposed exponential equations to illustrate the variation of the erosion rate in the erosion process.

Evapotranspiration (ET) plays an important role in integrated water resource planning, development and management. This process is particularly relevant in semiarid regions. The aim of the present study is to compare the actual spatial and temporal evapotranspiration (ETa) patterns and temporal trends in two semiarid forests, one in Brazil (Aiuaba) and the other in Spain (Valladolid). We used the Surface Energy Balance Algorithm for Land (SEBAL) to assess the effect of climatic variation in both areas. In the Brazilian semiarid forest, Caatinga is the main vegetation, while it is stone pine in Spain. For this purpose, 69 Landsat-5 and 42 Landsat-8 images (1995 – 2019) were used. The Mann-Kendall test was applied to assess the occurrence of trends in precipitation, temperature and potential evapotranspiration data; and the Temporal Stability Index (TSI) to know which areas have greater seasonal ETa. The annual amplitude of the potential evapotranspiration (ET0) is the same in both areas, however, the Caatinga values are higher. In the Caatinga forest, when ET0 presents its highest values throughout the year, ETa presents the lowest, and vice versa. In the Pinares forest, ETa follows the ET0 dynamics during the year, and the difference between ET0 and ETa is maximum during the summer. The Caatinga forest showed a greater spatial variation of ETa than the Pinares forest as well as a greater extension with lower temporal stability of ETa than the Pinares forest. Both the Caatinga forest and the Pinares forest showed significant annual trends of increase for ET0 and ETa: 3.5 mm and 2.2 mm, and 7.0 mm and 3.9 mm, respectively.

Evaporation is the key to the basin’s water cycle. Agricultural irrigation has resulted in a significant variation of regional potential evaporation (Epen). The spatiotemporal variation of Epen and the influencing factors in the natural, agricultural, and desert areas in different developmental stages of irrigation in the Heihe River Basin (HRB) from 1970 to 2017 are comparatively analyzed in this study. This work focused on the correction effect of irrigation on the variation of Epen. The agricultural water consumption in HRB significantly varied around 1998 due to the agricultural development and water policy. Under the influence of irrigation, the annual variation of Epen in the agricultural, natural, and desert areas was significantly different. From 1970 to 1998, the annual trend slope of Epen in the natural area only reduced by 1 mm decade-1, while that in the agricultural area significantly decreased by 39 mm decade-1. After the implementation of water-saving irrigation, the Epen in the natural and agricultural areas increased by 11 and 54 mm decade-1, respectively, from 1998 to 2017. In contrast with the natural and agricultural areas, Epen in the desert area decreased by 80 mm decade-1 from 1970 to 1998 and continuously decreased by 41 mm decade-1 from 1998 to 2017. However, the regulatory effect of irrigation on Epen in the desert area started to manifest due to the expansion of the cultivated land area in the desert area from 2010 to 2017. Irrigation has a significant regulatory effect on the variation of Epen in HRB. The regulatory effect is mainly reflected on the aerodynamic term (Eaero). The analytical results of the main meteorological factors affecting Epen in different regions indicated that the main meteorological factors influencing the variation of Epen in each region are the wind speed 2 m above the surface (U2) and the water vapor pressure difference (VPD).