Headwater Research Articles

Evaluation of driving effects of carbon storage change in the source of the Yellow River: A perspective with CMIP6 future development scenarios

Understanding how future climate scenarios impact land use/cover (LUC) and carbon storage (CS) is crucial for achieving carbon neutrality. However, research often overlooks the spatiotemporal impacts of future climate and socioeconomic changes on CS. This study integrates system dynamic (SD), patch-generating land use simulation (PLUS), the integrated valuation of ecosystem services and tradeoffs (InVEST) model, and the geographical detector to assess the LUC and CS evolution in the source of the Yellow River (SYR) from 2020 to 2060. Utilizing carbon density and LUC data, we explored the influence of natural and socioeconomic factors on CS under five shared socioeconomic pathways and representative concentration pathways (SSP-RCPs) scenarios. Our findings demonstrate that: (1) Ecological land, including woodland, grassland, and wetland, expanded more under SSP126 compared to SSP245, with SSP345, SSP460, and SSP585 showing a trend of degradation tied to deeper economic contribution. (2) By 2060, CS in terrestrial ecosystem under SSP126, SSP245, SSP345, SSP460, and SSP585 were 702.33 × 106 t, 700.33 × 106 t, 697.22 × 106 t, 696.03 × 106 t, and 691.21 × 106 t, respectively. This represents changes of 3.69 × 106 t, 1.69 × 106 t, −1.49 × 106 t, −2.68 × 106 t, and −7.43 × 106 t compared to 2020. (3) Soil type predominantly influenced the spatial differentiation of CS, with significant interactions with precipitation. This research provides new insights into land redistribution, economic strategies, and achieving carbon neutrality.

Geochemistry of Quaternary sediments in the northwestern South China Sea: Sediment provenance and mid-Pleistocene transition

The Quaternary sediments in the northwestern South China Sea (NW-SCS) provide valuable information about provenance, climate and sea level changes. However, the correlation between the geochemical records in marine sediments and these influencing factors remains less understood in the NW-SCS. Two wells penetrated Quaternary sediments on the shelf and shelf margin of the NW-SCS and provide an excellent dataset. In this study, the major, trace, and rare earth elements in the sediments were analyzed to reveal the Quaternary provenance changes that correlate with the climatic Middle Pleistocene transition (MPT). These results indicate that the core sediments were mainly derived from felsic source rocks and the degree of chemical weathering in the source areas is relatively low (CIA averaged at 58). The Quaternary provenance of the NW-SCS did not undergo significant changes, recording mixed sedimentation from the Red River, Hainan Island, and central Vietnamese sources. The felsic source rocks and negative Eu anomaly indicated the shelf area received sediments primarily from the Red River and Hainan Island. However, a positive Eu anomaly on the shelf margin suggests additional contributions from mafic rocks sourced from central Vietnam. During the MPT (1.3–1.4 to 0.8–0.9 Ma), the dominant periodicity of climate cycles changed from a 40 kyr obliquity cycle to a 100 kyr eccentricity cycle; the cooling climate led to a slight weaking in chemical weathering and a minor decrease in sediment supply from terrestrial sources. After the MPT, the mixed sourced sediments in the shelf and shelf margin areas of the NW-SCS likely suffered from multiple hydrodynamic forces under the influence of the Pleistocene high-frequency and high-amplitude sea level fluctuations. These climate induced changes led to significant fluctuations in element content that provide new insights into Quaternary sources and climatic events in the NW-SCS.

Formation, speciation, and temporal variability of DBPs in drinking water distribution systems in the context of ASR operations and extended storage periods

As climate change induces changes in water quality and available water quantity of drinking water supply sources, the final product water quality changes in terms of trace organics including disinfection byproducts (DBPs) formed during water treatment. In this study, the seasonal variability and speciation of DBPs across nine sample sites within a drinking water distribution system serving ∼400k people over a one-year period was investigated considering the governing parameters of water quality and treatment/transport/storage of finished water. The system considered treats surface water from a river and practices aquifer storage and recovery to address seasons water availability changes. Eighty-eight (88) sample sets were collected and held for 6-months in the laboratory to simulate extended storage scenarios associated with ASR operations, and each was analyzed at 9 different timesteps for concentration and speciation of chlorinated DBPs. Samples from groundwater influenced sites exhibited significantly lower total organic carbon (TOC) compared to other sites from the river source, and also were observed to have the lowest DBP formation. Three sites exceeded the Maximum Contaminant Level (MCL) for four total trihalomethanes (THM4) within 30–60 days of storage. Chloroform was the predominant THM4 species, even in groundwater-influenced locations, whereas di- and tri-chloroacetic acid (DCA and TCA) were the most prevalent haloacetic acids (HAA5). Extended water age at one site, coupled with low initial chlorine concentrations exhibited higher initial THM4 concentrations and flat DBP formation curves. The study results provide new insights into DBP occurrence and fate in drinking water distribution systems which consider water storage such as in ASR.

Conceptual Blending Theory: The Case of ‘Flying Bus’ from Turkish

Based on current discussions on Conceptual Blending/Integration Theory (CIT) and Conceptual metaphor Theory (CMT), this study investigates the application of Conceptual Blending Theory to a Turkish scenario where a Turkish speaker conceptualises a dangerously speeding bus as flying and associates it with Turkish Airlines. The study emphasizes the role of conceptual blending in creating novel meanings online by integrating disparate conceptual elements, as well as highlighting the complementary nature of CIT and CMT in meaning construction. In our scenario, the speaker’s metaphoric utterance as a reaction to the overspeed of a bus was explained by the metaphor TOO FAST DRIVING IS FLYING, which inherits the superordinate metaphor FAST MOTION IS FLIGHT, which is entrenched in our cultural cognition. Through a conceptual blending network mentally activated by the conceptualisation of the speeding bus as if flying, we illustrated how selected elements from the source (bus and driver) and target (plane and pilot) spaces were projected onto the blended space. It was also shown that Vital Relations within the blending network like Space, Role, and Disanalogy compressed the relevant counterparts from the source and target spaces into new integrated concepts to create novel meanings in the emergent structure, emphasizing the danger involved in the situation in the scenario.

Response of stream habitat and microbiomes to spruce budworm defoliation: New considerations for outbreak management.

Defoliation by eastern spruce budworm is one of the most important natural disturbances in Canadian boreal and hemi-boreal forests with annual area affected surpassing that of fire and harvest combined, and its impacts are projected to increase in frequency, severity, and range under future climate scenarios. Deciding on an active management strategy to control outbreaks and minimize broader economic, ecological, and social impacts is becoming increasingly important. These strategies differ in the degree to which defoliation is suppressed, but little is known about the downstream consequences of defoliation and, thus, the implications of management. Given the disproportionate role of headwater streams and their microbiomes on net riverine productivity across forested landscapes, we investigated the effects of defoliation by spruce budworm on headwater stream habitat and microbiome structure and function to inform management decisions. We experimentally manipulated a gradient of defoliation among 12 watersheds during a spruce budworm outbreak in the Gaspésie Peninsula, Québec, Canada. From May through October of 2019-2021, stream habitat (flow rates, dissolved organic matter [DOM], water chemistry, and nutrients), algal biomass, and water temperatures were assessed. Bacterial and fungal biofilm communities were examined by incubating six leaf packs for five weeks (mid-August to late September) in one stream reach per watershed. Microbiome community structure was determined using metabarcoding of 16S and ITS rRNA genes, and community functions were examined using extracellular enzyme assays, leaf litter decomposition rates, and taxonomic functional assignments. We found that cumulative defoliation was correlated with increased streamflow rates and temperatures, and more aromatic DOM (measured as specific ultraviolet absorbance at 254 nm), but was not correlated to nutrient concentrations. Cumulative defoliation was also associated with altered microbial community composition, an increase in carbohydrate biosynthesis, and a reduction in aromatic compound degradation, suggesting that microbes are shifting to the preferential use of simple carbohydrates rather than more complex aromatic compounds. These results demonstrate that high levels of defoliation can affect headwater stream microbiomes to the point of altering stream ecosystem productivity and carbon cycling potential, highlighting the importance of incorporating broader ecological processes into spruce budworm management decisions.

From source to sink: part 1-characterization and Lagrangian tracking of riverine microplastics in the Mediterranean Basin.

The Mediterranean Sea is one of the most critically polluted areas due to its semi-enclosed structure and its highly anthropized shoreline. Rivers are significant vectors for pollutant transfers from the continental to the marine environment. In this context, a 3D Lagrangian simulation of the dispersion of riverine microplastics (MPs) was performed, which included the application of a recently developed model that reassessed the MP fluxes discharged by rivers. MP physical properties from river samples were further investigated to approximate vertical displacement in modeled ocean currents. The use of a high-resolution circulation model, integrating Stokes drift, turbulent diffusion, and MP sinking and rising velocities, enabled us to establish stock balances. Our simulation suggested that 65% of river inputs may be made of floating MPs drifting in the surface layer and 35% of dense MPs sinking to deeper layers. The Eastern Mediterranean tends to accumulate floating MPs, primarily originating from the Western Mediterranean Basin, where major river sources are concentrated. After 2 years of simulation, modeled stranding sequestered 90% of the MP inputs, indicating relatively short average residence times from a few days to months at most for particles at sea. Although spatial distribution patterns stabilized after this period and a steady state may have been approached, the surface concentrations we modeled generally remained below field observations. This suggested either an underestimation of sources (rivers and unaccounted sources), by a factor of 6 at most, or an overestimation of MP withdrawal through stranding, to be reduced from 90 to around 60% or less if unaccounted sinks were considered.

Utility of an Instantaneous Salt Dilution Method for Measuring Streamflow in Headwater Streams.

Streamflow records are biased toward large streams and rivers, yet small headwater streams are often the focus of ecological research in response to climate change. Conventional flow measurement instruments such as acoustic Doppler velocimeters (ADVs) do not perform well during low-flow conditions in small streams, truncating the development of rating curves during critical baseflow conditions dominated by groundwater inflow. We revisited an instantaneous solute tracer injection method as an alternative to ADVs based on paired measurements to compare their precision, efficiency, and feasibility within headwater streams across a range of flow conditions. We show that the precision of discharge measurements using salt dilution by slug injection and ADV methods were comparable overall, but salt dilution was more precise during the lowest flows and required less time to implement. Often, headwater streams were at or below the depth threshold where ADV measurements could even be attempted and transects were complicated by coarse bed material and cobbles. We discuss the methodological benefits and limitations of salt dilution by slug injection and conclude that the method could facilitate a proliferation of streamflow observation across headwater stream networks that are highly undersampled compared to larger streams.

Impacts of wastewater treatment plant effluents on dissolved inorganic carbon in highly urbanized karst rivers, Southwest China

Wastewater treatment plants (WWTPs) are an important manifestation of the impact of urbanization on aquatic ecosystems, and the influences of effluents discharge from WWTPs on receiving river carbon biogeochemical cycle processes has been a research hotspot. However, our knowledge about potential impacts of WWTP effluents on dissolved inorganic carbon (DIC) cycle in karst rivers is rather limited. This study investigates the water chemistry and carbon isotope composition (δ13CDIC) in the urbanized reach of a river that drains the world’s largest continuous karst region in Southwest China, in an attempt to determine the effects of WWTP effluents on karst river DIC cycle and source discrimination. The results reveal: (1) Partial pressure of dissolved carbon dioxide (pCO2) levels in the river increased noticeably during the dry and normal seasons after receiving WWTP effluents; (2) There existed an ionic ratio overlap between end-members of silicate rock weathering and WWTP effluents which requires caution in identifying end-members of rock weathering in urbanized karst rivers; (3) DIC in the highly urbanized karst rivers was affected by complex geochemical processes and these processes varied in different seasons; (4) The contribution of WWTP effluents to the riverine DIC pool was 21±13 %, 58±21 % and 66±33 % in the wet, dry, and normal seasons, respectively. These findings highlight the interference of WWTP effluents with DIC carbon cycling in the receiving karst rivers. Since DIC from WWTPs do not relate with consuming atmospheric or soil CO2, it is important to exclude their contribution from the watershed’s rock weathering carbon sink budget. Based on these findings, we insist that the role and effect of WWTP effluents should be carefully considered when examining DIC carbon source and cycling in rivers that drain urbanized watersheds with abundant wastewater treatment plants.

Streamflow diurnal fluctuation and driving mechanism of headwater stream in a semi-humid mountainous region

Diurnal fluctuation in streamflow during rainless periods provides valuable signals for the calibration of hydrological models and comprehension of hydrological processes. Previous research has primarily focused on this phenomenon in the context of single-factor analysis in the Mediterranean, Maritime, and Alpine climates of Middle Europe and Western US. This study is based on the Xitaizi Experimental Watershed (XEW), a typical mountainous headwater watershed situated in the semi-humid monsoon North China Plain. Seven years of high-frequency observation data were used to investigate the characteristics of streamflow diurnal fluctuation, its driving mechanisms, and the propagation pathways of these fluctuation signals through hillslope-riparian-stream. The results are as follows: (1) Streamflow exhibits diurnal fluctuation during rainless periods throughout the year, with variations up to 36% of the daily mean and distinct patterns in rainy (peak at night) and dry seasons (peak in the afternoon). Choosing the proper timing for daily discharge observation can reduce bias due to fluctuations. (2) In rainy seasons, the impact of discharge fluctuation is significant, particularly in years with lower discharge. Meanwhile, the soil moisture in both the hillslope and the riparian zone, and the groundwater level in the riparian zone exhibit a daytime decline and a nighttime rise. The groundwater level in the hillslope fluctuates with a lag time of approximately 6 to 9 hours. (3) Numerical simulations and cross-correlation analysis demonstrate that the dominant driving mechanism of diurnal fluctuations in rainy seasons is the diurnal evapotranspiration variation in the riparian zone, while the influence of aquifer hydraulic conductivity is insignificant.

Nonnegligible contribution of terrigenous sediment inputs from local small watersheds to west regions of the Pearl River Estuary, northern South China Sea shelf

As a crucial “sink” for terrigenous material entering the ocean, provenance of sediments within the coastal zone and continental shelf sea regions holds significant scientific importance in the investigation of global material cycling. Environmental magnetism was proved as an effective and rapid approach for sediment source identification. Detail and systematic magnetic measurements were performed for surface sediment samples collected from the mega Pearl River, local small rivers (Tan, Moyang and Jian rivers) of west Guangdong, coastal zone (CZ) and continental shelf (CS) to analyze the contribution of local small watersheds to marine sediments. The results indicate that detrital river input magnetite and hematite are coexisted in both CZ and CS sediments. Compared to CZ sediments, relatively higher concentration of hematite and finer grain size of magnetite are appeared at CS sediments. By comparing of magnetic parameters, it was inferred that magnetic minerals from the Pearl and Tan rivers are transported and deposited on the coastal zone by Guangdong longshore current. Meanwhile, sediment magnetic parameters in the Moyang and Jian Rivers are similar to the CS sediments, implying the two rivers-sourced materials were directly transported and deposited at the CS due to their narrow and restricted estuaries, and/or the CS preserves the residual deposits from the two rivers formed during the Last Glacial. Except for the Pearl River, sources of local small rivers significantly contribute to marine sediments at the coastal zone and continental shelf.

Difference of habitat suitability and the influencing variables between winter and summer of Procapra picticaudata in the Three-River-Source region, China.

Procapra picticaudata is an ungulate endemic to the Tibetan Plateau and is widely distributed in the Three-River-Source region. Predicting the seasonal variations in habitat suitability and understanding the effects of environmental variables on habitat use by this species will help formulate effective conservation strategies and clarify its niche characteristics. Based on point records of the occurrence collected during repeated field surveys in winter (January 2019) and summer (August 2019), we used MaxEnt model to predict the differences in habitat suitability and the distribution pattern of the P. picticaudata in the Three-River-Source region using eight preselected environmental variables. We further explored the influence of those variables on the P. picticaudata' distribution pattern using environmental response curves. The results showed that the average area under the receiving operator curve values in winter and summer was 0.901±0.023 and 0.882±0.024, respectively, with a good accuracy of fitness. The total area of suitable habitat for P. picticaudata in winter and summer was 6.83×104 and 9.78×104 km2, respectively. The area of suitable habitats in summer increased significantly compared with winter. There was a tendency for P. picticaudata to spread to the south of the Yangtze River Source Park and the Yellow River Source Park in summer. The spatial patterns of habitat suitability in both winter and summer took Three-River-Source National Park as the high-value center and decreased around it. The seasonal average temperature, altitude, population density, and slope were the main environmental variables affecting the distribution of P. picticaudata both in winter and summer. The higher temperatures in summer allowed the suitable P. picticaudata habitats to extend into areas above 5000 m in altitude, and to areas with slopes of less than 25°, compared with winter. The expansion of human activities in summer encroached on the suitable habitat of P. picticaudata.

Comparison of freshwater diatom assemblage between old-growth broad-leaved and planted coniferous forest basins in temperate region, Japan

Various forest types are distributed in headwater streams. However, differences in diatom assemblages among forest types in Japan have not been thoroughly investigated. The objective of this study was to determine differences in diatom assemblages in the most common forest types in Japanese headwater streams, old-growth broadleaf forest (OBF) and planted coniferous forest (PCF) types, and to identify diatom species that tend to grow in either the OBF or PCF forest types. Diatom abundance differed between the forest types, but the numbers of species, genera and families did not. Nonmetric multidimensional scaling analysis revealed the differences in diatom assemblages in OBF and PCF types and this difference was brought by particularly of some genera such as Gomphonema, Planothidium and Navicula. Differences in diatom assemblages between the two forest types were considered to be a reflection of the different environmental conditions such as light condition and alkalinity, created by the different forest types.

The role of the environment and connectivity on multiple facets of local fish diversity in tropical headwater streams

Abstract The identification of multiple facets of biodiversity (e.g., phylogenetic and functional) can help to understand how evolutionary and ecological mechanisms shape the assembly of biological communities. Here, we employed multiple regressions and variance partitions to investigate the effects of environmental conditions, connectivity and space on aspects of the functional and phylogenetic facets of fish fauna in tropical headwater streams of the Xingu River basin, in Eastern Amazonia. We found that the functional and phylogenetic diversities of fish communities are related to local environmental conditions and stream connectivity in the drainage network, with marked differences occurring between the rainy and dry periods. Furthermore, we discovered that functional uniqueness was influenced mainly by environmental factors, whereas phylogenetic uniqueness had a more complex relationship with the influence of local environmental factors and connectivity. Our findings indicate that the fish assemblages of small headwater streams of the Xingu River basin share a close phylogenetic history. This is probably because of the climatic and environmental stability experienced by Amazonian ichthyofauna over evolutionary time. Our findings emphasise the role of niche‐based processes in shaping the unique functional composition of fish assemblages in headwater streams, and highlight the importance of environmental heterogeneity in maintaining the ecological integrity of these freshwater ecosystems.

Wildfires Influence Mercury Transport, Methylation, and Bioaccumulation in Headwater Streams of the Pacific Northwest.

The increasing frequency and severity of wildfires are among the most visible impacts of climate change. However, the effects of wildfires on mercury (Hg) transformations and bioaccumulation in stream ecosystems are poorly understood. We sampled soils, water, sediment, in-stream leaf litter, periphyton, and aquatic invertebrates in 36 burned (one-year post fire) and 21 reference headwater streams across the northwestern U.S. to evaluate the effects of wildfire occurrence and severity on total Hg (THg) and methylmercury (MeHg) transport and bioaccumulation. Suspended particulate THg and MeHg concentrations were 89 and 178% greater in burned watersheds compared to unburned watersheds and increased with burn severity, likely associated with increased soil erosion. Concentrations of filter-passing THg were similar in burned and unburned watersheds, but filter-passing MeHg was 51% greater in burned watersheds, and suspended particles in burned watersheds were enriched in MeHg but not THg, suggesting higher MeHg production in burned watersheds. Among invertebrates, MeHg in grazers, filter-feeders, and collectors was 33, 48, and 251% greater in burned watersheds, respectively, but did not differ in shredders or predators. Thus, increasing wildfire frequency and severity may yield increased MeHg production, mobilization, and bioaccumulation in headwaters and increased transport of particulate THg and MeHg to downstream environments.

Stable isotopes reveal soil evaporation and its controlling factors in the Heihe River source area on the northeastern Qinghai-Tibetan Plateau

Study regionThe Heihe River source area in the Northeastern Qinghai-Tibetan Plateau, China. Study focusSoil evaporation, which is a key process in soil water loss, is influenced by various environmental factors. However, the identification of its main drivers on a large scale in alpine mountains remains challenging due to sampling constraints. This study examined the spatial distribution of soil evaporation and control factors during the growing season in the Heihe River source area. New hydrological insightsThe results indicated that soil evaporation, represented by lc-excess values, gradually increased from southeast to northwest, and then decreased, reaching a depth of 50 cm below the surface. Although the normalized difference vegetation index explained 54 % of the spatial variation in soil evaporation, the interaction between land surface temperature and soil water content (SWC) provided a more robust explanation. The soil evaporation losses exhibited the following pattern: cropland > grassland > forest land > shrubland. In forest land and shrubland, SWC and precipitation explained 68 % and 73.3 % of the spatial variations in soil evaporation, respectively. Grassland mainly relied on temperature and SWC, with 49.33 % of unexplained spatial variability by environmental factors. Meanwhile, the aridity index and aspect explained 45 % and 44.6 % of the spatial variations in cropland. These findings provided invaluable information for advancing our understanding of the ecohydrological processes in alpine mountains.

Influence of Adding Small Instream Wood on Fishes and Hydraulic Conditions in Channelized Agricultural Headwater Streams

Influence of Adding Small Instream Wood on Fishes and Hydraulic Conditions in Channelized Agricultural Headwater Streams

Four decades of changing dissolved organic matter quality and stoichiometry in a Swedish forest stream

Dissolved organic matter (DOM) concentrations have risen by a factor of two or more across much of Europe and North America during recent decades. These increases have affected the carbon cycle, light regime, drinking water treatability, and the energy and nutrient budgets of lakes and streams. However, while trends in DOM quantity are well characterised, information on how/whether qualitative properties of DOM have changed are scarce. Here, we describe over 40 years of monitoring data from a forested headwater stream in the Gårdsjön experimental catchment, southwest Sweden, which provides a unique record of biogeochemical change, including optical and stoichiometric DOM quality metrics, spanning the entire period of recovery from acidification. For the period 1980–2020 we find a 71% reduction in decadal mean sulphate concentrations, and a similar reduction in inorganic aluminium concentrations, alongside a 64% increase in dissolved organic carbon (DOC) concentrations. Over the same period, colour (absorbance at 420 nm) increased almost twice as much as DOC, whereas dissolved organic nitrogen (DON) increased by only one third as much. These results demonstrate a shift in stream water composition, with DOM becoming dominated by highly coloured, complex, nitrogen-poor compounds. This material is likely more resistant to biological degradation, but more susceptible to photochemical degradation. Changes in DOM stoichiometry could lead to intensified nitrogen and/or phosphorus limitation in surface waters, while increased colour/DOC ratios could intensify light-limitation of primary production beyond that expected from DOC increases alone. We observed increases in organic matter associated metals (iron 117%, organically complexed aluminium 85%) that exceeded the increase in DOC, consistent with their increased mobilisation by more aromatic organic matter. All observed changes are consistent with recovery from acidification being the primary driver of change, implying that past acidification, and ongoing recovery, have profoundly affected terrestrial and aquatic biogeochemistry, ecology and the carbon cycle.

Insect Herbivores, Plant Sex, and Elevated Nitrogen Influence Willow Litter Decomposition and Detritivore Colonization in Early Successional Streams

Headwater streams are reliant on riparian tree leaf litterfall to fuel brown food webs. Terrestrial agents like herbivores and contaminants can alter plant growth, litter production, litter quality, and the timing of litterfall into streams, influencing aspects of the brown food web. At Mount St. Helens (USA), early successional streams are developing willow (Salix sitchensis) riparian zones. The willows are attacked by stem-boring herbivores, altering litter quality and the timing of litterfall. Within a established experimental plots, willows (male and female plants) were protected from herbivores using insecticides and provided with experimental additions of nitrogen. This enabled us to test the interacting influences of herbivores, nitrogen deposition, and willow sex on leaf litter quality, aquatic litter decomposition, and microbial and invertebrate detritivores. We found weak litter quality effects (higher N and lower C:N) for the herbivore treatment, but no effect of nitrogen deposition. Although litter decomposition rates were not strongly affected by litter treatments, detritivore communities were altered by all treatments. Nitrogen deposition resulted in decreased bacterial richness and decreased fungal diversity in-stream. Aquatic macroinvertebrate communities were influenced by the interacting effects of herbivory and nitrogen addition, with abundances highest in herbivore litter with the greatest N addition. Shredders showed the highest abundance in male, herbivore-attacked litter. The establishment of riparian willows along early successional streams and their interacting effects with herbivores and nitrogen deposition may be influencing detritivore community assembly at Mount St. Helens. More broadly, global changes like increased wet and dry N deposition and expanded ranges of key herbivores might influence tree litter decomposition in many ecosystems.

A novel error decomposition and fusion framework for daily precipitation estimation based on near-real-time satellite precipitation product and gauge observations

Near-real-time satellite precipitation products (SPPs) possess inherent application prospects in the hydro-meteorological field due to their convenient acquisition and accessibility. Integrating gauge-based measurements with near-real-time SPPs is an effective approach for achieving precise spatial precipitation estimates at daily scale. This study proposed a newly developed error decomposition and fusion framework, named EDGWR, which integrates error decomposition and geographically weighted regression (GWR). The final merged product, denoted as IMERG-EDGWR, was obtained from the near-real-time Integrated Multi-satellitE Retrievals for Global Precipitation Measurement Early Run (IMERG-E) product. IMERG-EDGWR was compared with the raw IMERG-E, near-real-time IMERG-L, post-real-time IMERG-F, global multi-source merged precipitation data (MSWEP), interpolated results (IDW and OK), and direct application of GWR outcomes (IMERG-GWR), utilizing the daily ground measurements from 12 meteorological stations located in the Yellow River source region (YRSR). The evaluation results from 2014 to 2018 revealed that IMERG-EDGWR exhibited significant enhancements over the raw IMERG-E, surpassed the research-level IMERG-F, and generally outperformed IDW, OK, MSWEP, and IMERG-GWR. Notably, IMERG-EDGWR enhances the detection of heavy precipitation events, refining estimates of both magnitude and frequency for precipitation over 25 mm. During the winter season, IMERG-EDGWR produced the most accurate precipitation estimates with notable improvement of precipitation detection capabilities. An experiment reducing input data by excluding gauge observations from the GPCC dataset tested the robustness of the EDGWR algorithm, confirming its superiority even with diminished input data. The merging framework proposed in this study constitutes an efficacious and implementable solution to enhance the accuracy of near-real-time SPPs and is expected to be implemented in different regions in future research.

Optimization of floodwater redistribution from Lake Nasser could recharge Egypt’s aquifers and mitigate its excessive floods

Extreme precipitation periods, possibly related to climate change, over the Nile River source areas caused flooding in Sudan and excess runoff reaching Lake Nasser in Egypt in 1998–2002 and 2019–2022. Excess water from the 1st event (25.5 × 109 m3) was channeled to depressions within the plateau west of the Nile Valley, forming the Tushka Lakes, where it was left to evaporate, a fate that awaits the 53.5 × 109 m3 from the 2nd event while the underlying fossil Nubian Sandstone Aquifer System is being depleted (−0.98 × 109 m3/yr). We simulated release scenarios of excess Lake Nasser waters (53.5 × 109 m3) to proximal lowlands; preference was given to the scenario that recharged the aquifer through infiltration (74.3%) and minimized losses to evaporation (20.1%) and surface runoff (5.6%). Findings serve as an example of adaptations that replace catastrophic consequences of climate change with beneficial and sustainable development opportunities.