Ontological and epistemological commitments in interdisciplinary water research: Uncertainty as an entry point for reflexion

Against the background of a renewed interest in interdisciplinary water research, we begin this paper by diagnosing a need for deeper engagement at the epistemological and ontological level. We then analyse the ontological and epistemological commitments of three modeling examples: an academic human-flood model, a nutrient transfer decision support model and a policy facing water security model. These examples demonstrate how research practices are not neutral but intervene in the world by distributing agency unequally, providing naturalized and de-politicized explanations of the past and pre-configuring certain futures while foreclosing others. Lastly, we position hydrology's uncertainty tradition and its problematisation of choices in the research process as an entry point for reflexion on the contingencies of and ethical responsibility for research practices. This uncertainty tradition provides more common ground for collaboration between hydrologists and critical water researchers than previously acknowledged, while such collaboration would still thrive on confrontation. We conclude with a call for greater humility in water research, especially when using models, and practical suggestions for how researchers could uncover ontological and epistemological commitments and live up to the ethical responsibility they entail.Peer Reviewe

Conventional and makeshift rainwater harvesting in rural South Africa: exploring determinants for rainwater harvesting mode

This article was supported by the Open Access Publication Fund of Humboldt-Universität zu Berlin.In underserved rural areas, domestic rainwater harvesting has been gaining importance as an alternative water source. In rural South Africa, however, less than 1% of households use conventional rainwater harvesting systems. Instead, a household survey in KwaZulu-Natal reveals that many households harvest rainwater in a makeshift manner, using homemade gutters and drums. Statistical analysis shows that high income, a brick house with straight gutters and good water services facilitate conventional rainwater harvesting, while a household with only round huts is easily trapped into makeshift rainwater harvesting. For upscaling rainwater harvesting in rural areas, housing types need to be considered.Peer Reviewe

Contrasting controls on the phosphorus concentration of suspended particulate matter under baseflow and storm event conditions in agricultural headwater streams

Whilst the processes involved in the cycling of dissolved phosphorus (P) in rivers have been extensively studied, less is known about the mechanisms controlling particulate P concentrations during small and large flows. This deficiency is addressed through an analysis of large numbers of suspended particulate matter (SPM) samples collected under baseflow (n = 222) and storm event (n = 721) conditions over a 23-month period across three agricultural headwater catchments of the River Wensum, UK. Relationships between clay mineral and metal oxyhydroxide associated elements were assessed and multiple linear regression models for the prediction of SPM P concentration under baseflow and storm event conditions were formulated. These models, which explained 71–96% of the variation in SPM P concentration, revealed a pronounced shift in P association from iron (Fe) dominated during baseflow conditions to particulate organic carbon (POC) dominated during storm events. It is hypothesised this pronounced transition in P control mechanism, which is consistent across the three study catchments, is driven by changes in SPM source area under differing hydrological conditions. In particular, changes in SPM Fe–P ratios between small and large flows suggest there are three distinct sources of SPM Fe; surface soils, subsurface sediments and streambed iron sulphide. Further examination of weekly baseflow data also revealed seasonality in the Fe–P and aluminium oxalate–dithionate (Alox–Aldi) ratios of SPM, indicating temporal variability in sediment P sorption capacity. The results presented here significantly enhance our understanding of SPM P associations with soil derived organic and inorganic fractions under different flow regimes and has implications for the mitigation of P originating from different sources in agricultural catchments

Collective payments for ecosystem services

Payments for ecosystem services (PES) gained an increasing importance in science and politics within the last decades. Although the enthusiasm about PES is particularly high in Environmental Economics, opponents criticize the market-based character of PES and the associated commodification as well as privatization trends. By means of a systematic literature review we aim at shedding light on the complex and controversial debate about how to define commodification and related privatization processes and how they are linked to PES outcomes. We do so by setting a particular focus on the potentials and challenges of community-based and collective PES (C-PES), also in contrast to PES targeting land under private land tenure (P-PES). Our results reveal that C-PES show promising results when targeting local communities with a high level of social capital. However, there is a lack of studies that systematically assess the relations between different degrees of commodification and the ecological and social outcome of PES programs. For this reason, we provide a new conceptual framework of commodification by highlighting two interrelated spheres, where PES-related commodification processes take place: The first sphere relates to the commodification of ES-providing land, which greatly depends on the land tenure regime in place. The second sphere addresses the commodification of ecosystem services (ES). Our review indicates that C-PES show rather low degrees of commodification in the first sphere because the ES-providing land is often less embedded into private land markets. This is due to often missing alienation rights, more complex decision-making processes, and a potentially lower profit-orientation of the landowners. Empirical long-term studies are needed to investigate changes in both spheres of commodification over time, their potential interactions, and how they affect the outcome of C-PES and P-PES programs.Peer Reviewe

Benchmarking inference methods for water quality monitoring and status classification

River water quality monitoring at limited temporal resolution can lead to imprecise and inaccurate classification of physicochemical status due to sampling error. Bayesian inference allows for the quantification of this uncertainty, which can assist decision-making. However, implicit assumptions of Bayesian methods can cause further uncertainty in the uncertainty quantification, so-called second-order uncertainty. In this study, and for the first time, we rigorously assessed this second-order uncertainty for inference of common water quality statistics (mean and 95th percentile) based on sub-sampling high-frequency (hourly) total reactive phosphorus (TRP) concentration data from three watersheds. The statistics were inferred with the low-resolution sub-samples using the Bayesian lognormal distribution and bootstrap, frequentist t test, and face-value approach and were compared with those of the high-frequency data as benchmarks. The t test exhibited a high risk of bias in estimating the water quality statistics of interest and corresponding physicochemical status (up to 99% of sub-samples). The Bayesian lognormal model provided a good fit to the high-frequency TRP concentration data and the least biased classification of physicochemical status (< 5% of sub-samples). Our results suggest wide applicability of Bayesian inference for water quality status classification, a new approach for regulatory practice that provides uncertainty information about water quality monitoring and regulatory classification with reduced bias compared to frequentist approaches. Furthermore, the study elucidates sizeable second-order uncertainty due to the choice of statistical model, which could be quantified based on the high-frequency data.Peer Reviewe

High-temporal Resolution Sediment Fingerprinting in the River Wensum Demonstration Test Catchment, UK: A Bayesian Approach

A high-temporal resolution fluvial sediment source apportionment model, set within an empirical Bayesian framework, is presented for the River Wensum Demonstration Test Catchment (DTC), UK. Direct X-ray fluorescence (XRF) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) analysis of sediment covered filter papers were used in conjunction with ISCO automatic water samplers to monitor suspended particulate matter (SPM) geochemistry at high-temporal resolution throughout the progression of five heavy precipitation events during 2012-2013. Exploiting the spatial and temporal variation in four potential sediment source areas and SPM geochemistry respectively, we are able to apportion sediment contributions from eroding stream channel banks, arable topsoils, damaged road verges and agricultural field drains at 60-120 minute resolution. For all monitored precipitation episodes, pre- and post-event conditions are dominated by elevated SPM calcium concentrations that indicate major sediment inputs from carbonate-rich subsurface sources. Conversely, precipitation events coincide with an increase in concentrations of clay-associated elements and a consequent increase in predicted contributions from surface sources. Employing a Gibbs sampling Markov Chain Monte-Carlo mixing model procedure has enabled full characterisation of both spatial geochemical variability and instrument precision to quantify uncertainty around posterior distributions. All model source apportionment estimates correspond favourably with understanding of the regional geology, analysis of hysteresis behaviour, and visual observations of catchment processes. The results presented here demonstrate how to directly analyse SPM trapped on filter papers by spectroscopy to yield the high-temporal resolution source apportionment estimates required by catchment managers to help mitigate the deleterious effects of land-to-river sediment transfer

Combining Two Filter Paper-Based Analytical Methods to Monitor Temporal Variations in Fluvial Suspended Solid Properties

Many of the commonly used analytical techniques for assessing the properties of fluvial suspended solids are neither cost-effective nor time-efficient, making them prohibitive to long-term high-resolution monitoring.We propose a novel methodology utilising two types of spectroscopy which, when combined with automatic water samplers, can generate accurate, high-temporal resolution sediment property data, inexpensively and non-destructively, directly from sediment covered filter papers. A dual X-ray fluorescence spectroscopy (XRFS) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) approach is developed to estimate concentrations for a range of elements (Al, Ca, Ce, Fe, K, Mg, Mn, Na, P, Si, Ti) and compounds (organic carbon, Aldithionate, Aloxalate, Fedithionate, and Feoxalate) within sediments trapped on quartz fibre filters at masses as low as 3 mg. Calibration models with small prediction errors are produced for a total of 16 elements and compounds for which the geochemical signal is demonstrated to be time stable enabling samples to be stored for several weeks prior to analysis. Spectral pre-processing methods are shown to enhance the reproducibility of results for some compounds, whilst corrections for sediment mass retention are derived, and the importance of filter paper selection and homogeneous sample preparation in minimising spectral interference are emphasized. The results presented here demonstrate the potential for a combined XRFS and DRIFTS analysis of sediment covered filter papers to be utilized under a range of in-stream hydrological conditions where there is an environmental requirement for high-resolution monitoring of suspended solid properties

Will PES Schemes Survive in the Long-term Without Evidence of Their Effectiveness? Exploring Four Water-related Cases in Colombia

Unidad de excelencia María de Maeztu MdM-2015-0552This paper explores the reasons why payers, intermediaries, and providers engage in PES even under uncertainty about outcomes, and how they relate to the long term durability of the scheme. In theory, it is expected that, in face of high uncertainty, payers would leave the projects if effectiveness cannot be demonstrated and providers would not keep their conservation practices if no money remains available. Consequently, it is also expected that PES proponents would do their best to demonstrate ES improvement/maintenance. To explore these hypotheses we use field data collected from PES schemes in Colombia. Our results show that payers have additional motivations for engaging beyond ES improvement (e.g., CSR, green image). These motivations may explain their permanence in the scheme even without evidence of effectiveness. Water quantity/quality concerns were the main driver for participation of providers, evidencing that they do not see themselves only as providers but also as users. Therefore, the lack of evidence of effectiveness could discourage their permanence. Intermediaries are the ones mostly concerned about presenting evidence of PES effectiveness for many reasons (e.g. reputation, engaging stakeholders). PES may survive in the long term due to additional motivations from stakeholders, however, evidence of effectiveness is still expected

The world’s growing municipal solid waste: trends and impacts

Global municipal waste production causes multiple environmental impacts, including greenhouse gas emissions, ocean plastic accumulation, and nitrogen pollution. However, estimates of both past and future development of waste and pollution are scarce. We apply compositional Bayesian regression to produce the first estimates of past and future (1965–2100) waste generation disaggregated by composition and treatment, along with resultant environmental impacts, for every country. We find that total wastes grow at declining speed with economic development, and that global waste generation has increased from 635 Mt in 1965 to 1999 Mt in 2015 and reaches 3539 Mt by 2050 (median values, middle-of-the-road scenario). From 2015 to 2050, the global share of organic waste declines from 47% to 39%, while all other waste type shares increase, especially paper. The share of waste treated in dumps declines from 28% to 18%, and more sustainable recycling, composting, and energy recovery treatments increase. Despite these increases, we estimate environmental loads to continue increasing in the future, although yearly plastic waste input into the oceans has reached a peak. Waste production does not appear to follow the environmental Kuznets curve, and current projections do not meet UN SDGs for waste reduction. Our study shows that a continuation of current trends and improvements is insufficient to reduce pressures on natural systems and achieve a circular economy. Relative to 2015, the amount of recycled waste would need to increase from 363 Mt to 740 Mt by 2030 to begin reducing unsustainable waste generation, compared to 519 Mt currently projected