16 research outputs found
Sediment respiration pulses in intermittent rivers and ephemeral streams
Intermittent rivers and ephemeral streams (IRES) may represent over half the global stream network, but their contribution to respiration and carbon dioxide (CO2) emissions is largely undetermined. In particular, little is known about the variability and drivers of respiration in IRES sediments upon rewetting, which could result in large pulses of CO2. We present a global study examining sediments from 200 dry IRES reaches spanning multiple biomes. Results from standardized assays show that mean respiration increased 32–66‐fold upon sediment rewetting. Structural equation modelling indicates that this response was driven by sediment texture and organic matter quantity and quality, which, in turn, were influenced by climate, land use and riparian plant cover. Our estimates suggest that respiration pulses resulting from rewetting of IRES sediments could contribute significantly to annual CO2 emissions from the global stream network, with a single respiration pulse potentially increasing emission by 0.2–0.7%. As the spatial and temporal extent of IRES increases globally, our results highlight the importance of recognizing the influence of wetting‐drying cycles on respiration and CO2 emissions in stream networks
A global analysis of terrestrial plant litter dynamics in non-perennial waterways
Perennial rivers and streams make a disproportionate contribution to global carbon (C) cycling. However, the contribution of intermittent rivers and ephemeral streams (IRES), which sometimes cease to flow and can dry completely, is largely ignored although they represent over half the global river network. Substantial amounts of terrestrial plant litter (TPL) accumulate in dry riverbeds and, upon rewetting, this material can undergo rapid microbial processing. We present the results of a global research collaboration that collected and analysed TPL from 212 dry riverbeds across major environmental gradients and climate zones. We assessed litter decomposability by quantifying the litter carbon-to-nitrogen ratio and oxygen (O2) consumption in standardized assays and estimated the potential short-term CO2 emissions during rewetting events. Aridity, cover of riparian vegetation, channel width and dry-phase duration explained most variability in the quantity and decomposability of plant litter in IRES. Our estimates indicate that a single pulse of CO2 emission upon litter rewetting contributes up to 10% of the daily CO2 emission from perennial rivers and stream, particularly in temperate climates. This indicates that the contributions of IRES should be included in global C-cycling assessments
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Measuring household consumption and waste in unmetered, intermittent piped water systems
Measurements of household water consumption are extremely difficult in intermittent water supply (IWS) regimes in low- and middle-income countries, where water is delivered for short durations, taps are shared, metering is limited, and household storage infrastructure varies widely. Nonetheless, consumption estimates are necessary for utilities to improve water delivery. We estimated household water use in Hubli-Dharwad, India, with a mixed-methods approach combining (limited) metered data, storage container inventories, and structured observations. We developed a typology of household water access according to infrastructure conditions based on the presence of an overhead storage tank and a shared tap. For households with overhead tanks, container measurements and metered data produced statistically similar consumption volumes; for households without overhead tanks, stored volumes underestimated consumption because of significant water use directly from the tap during delivery periods. Households that shared taps consumed much less water than those that did not. We used our water use calculations to estimate waste at the household level and in the distribution system. Very few households used 135 L/person/d, the Government of India design standard for urban systems. Most wasted little water even when unmetered, however, unaccounted-for water in the neighborhood distribution systems was around 50%. Thus, conservation efforts should target loss reduction in the network rather than at households
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From Intermittent to Continuous Water Supply A Household-level Evaluation of Water System Reforms in Hubli–Dharwad
Employingamatchedcohortresearchdesign,eight wardswithintermittentwatersupply arecomparedto eightwardsupgradedtocontinuous(24x7)supplyina demonstrationprojectinHubli–Dharwad,Karnataka, withrespecttotapwaterquality,childhealth, waterstoragepractices,andcopingcostsacross socio-economicstrata.Waterconsumptionandwastein theintermittentzones,andthepotentialforscale-upof continuoussupplytotheentirecity,areestimated.Itwas foundthatthe24x7projectimprovedwaterquality,did notimproveoverallchildhealth,butdidreduceserious waterborneillnessesinthelowest-incomestrata, reducedthecostsofwaiting,increasedmonthlywater bills,andpotentiallyreducedwatersecurityforsomeof thepooresthouseholds
Recommended from our members
From Intermittent to Continuous Water Supply A Household-level Evaluation of Water System Reforms in Hubli–Dharwad
Employingamatchedcohortresearchdesign,eight wardswithintermittentwatersupply arecomparedto eightwardsupgradedtocontinuous(24x7)supplyina demonstrationprojectinHubli–Dharwad,Karnataka, withrespecttotapwaterquality,childhealth, waterstoragepractices,andcopingcostsacross socio-economicstrata.Waterconsumptionandwastein theintermittentzones,andthepotentialforscale-upof continuoussupplytotheentirecity,areestimated.Itwas foundthatthe24x7projectimprovedwaterquality,did notimproveoverallchildhealth,butdidreduceserious waterborneillnessesinthelowest-incomestrata, reducedthecostsofwaiting,increasedmonthlywater bills,andpotentiallyreducedwatersecurityforsomeof thepooresthouseholds