Entire Basin Research Articles

Water mass age and dissolved organic matter properties drive the diversity of pelagic prokaryotes in the Western Mediterranean Sea

The deep sea is among the largest, yet still poorly known, ecosystems on Earth. This knowledge gap is particularly evident for the bathypelagic layer (between 1000 and 4000 m) of the deep Mediterranean Sea (MS), characterized by peculiar environmental conditions at meso- and bathypelagic depths, such as the thermal signature of the deep waters, showing temperatures approximately 10 °C higher than any oceanic system at comparable depths. This sustains high rates of prokaryotic activities and fast dissolved organic matter (DOM) mineralization rates, and likely selects for unique microbial assemblages. We collected seawater samples in stations representative of different areas of the Western Mediterranean Sea (Algero-Provençal Basin, Alboran Sea and Gulf of Lion), from the surface to the bathypelagic layer (down to 2680 m) and in different water masses, and described the composition of pelagic prokaryotic communities, along with measurements of the main physical-chemical variables, concentration and optical properties (absorption and fluorescence) of DOM. Remarkable differences in DOM optical properties were observed among water masses, with highest dissolved organic carbon (DOC) values in surface waters and lowest in the oldest water masses represented by the Western Mediterranean Deep Water (WMDW) and the Levantine Intermediate Water (LIW), which were characterized by the highest concentration of recalcitrant DOM. The water mass had a significant partitioning effect on microbial community composition, which showed the highest richness in LIW. DOC, the marine humic-like component of DOM (C1mh) and oxygen were the main drivers of prokaryotic community structure. Changes in quality of DOM were reflected in shifts in community composition, supporting the existence of strong relationships between DOM quality and microbial community composition in the deep MS. Our data shed light on the community composition and diversity patterns of prokaryotic plankton in the deep western MS, helping to elucidate the major microbial players in the DOM cycling, and to progress towards a better comprehension of its future trends in light of changing conditions that are modifying the oceanography of the entire MS basin.

Assessment of Meteorological Drought under the Climate Change in the Kabul River Basin, Afghanistan

Kabul River Basin is one of the most significant river basins in Afghanistan from a socio-economic perspective. Since the country is located in an arid climate zone with drastically varying climatic behavior, an effective assessment of meteorological drought is very essential to managing the limited availability of water resources. For this endeavor, the outputs of three general circulation models under two representative concentration pathways (RCP 4.5 and RCP 8.5) were used against the baseline period of 1961–1980. Different bias correction methods were applied, and the results show that the delta change method, quantile mapping method, and empirical quantile mapping all performed better for the precipitation, maximum temperature, and minimum temperature datasets, respectively. The ERA5-Land datasets and WorldClim Version 2 are used to validate the bias-corrected precipitation and temperature datasets, respectively, to determine their dependability, and the results were found to be promising. Standardized Precipitation Index (SPI), Reconnaissance Drought Index (RDI), Deciles Index (DI), and New Drought Index (NDI) were used to assess the drought condition in the past and forecast for the future periods of the 2020s, 2050s, and 2080s. The spatial distribution of assessed drought indices was mapped using the inverse distance weighting (IDW) method. Our results revealed that moderate to extreme droughts are consistent across the entire basin. This might be because the projected annual precipitation in the river basin shows a decline of 53–65% up to the end of this century (2100), and the average annual temperature is projected to increase by 1.8 °C, 3.5 °C, and 4.8 °C, respectively, for the three future periods of the 2020s, 2050s, and 2080s. Furthermore, the results show that the drought estimated by SPI and RDI for future climate scenarios is almost the same, whereas NDI estimates frequent drought events after the 2050s. However, for moderate drought, RDI, which includes the effects of evapotranspiration, was found to be far greater than SPI under both scenarios, and NDI considering temperature and precipitation also estimates a larger number of drought years, strengthening the possibility of its occurrence in the basin. A regional comparison of drought also indicates a decrease in precipitation in future periods, predominantly in high altitudes.

Spatial Variations in Tropical Cyclone Rainfall over the Western North Pacific According to ENSO Phase

Abstract This study investigated spatial variations in rainfall accompanying tropical cyclones (TCs) over the western North Pacific (WNP) from June to October over 1998–2019 according to phases of El Niño–Southern Oscillation (ENSO). The rainfall characteristics of TCs include rainfall strength (RS) in the core region, total rainfall area (RA), and total rainfall volume (RV), all of which were calculated from satellite precipitation data. Spatial variation in mean RS presents a west–east dipole pattern (i.e., increases in the west of 125°E and decreases in the east during La Niña, and vice versa during El Niño) similar to that of maximum wind speed (Vmax), indicating a close relationship between them. On the other hand, both of mean RA and RV homogeneously increase during La Niña over the entire basin while they decrease during El Niño. The environmental conditions around TCs, including sea surface temperature, total column water, and divergence in the upper and lower troposphere during La Niña appear generally favorable for precipitation, while those during El Niño are unfavorable. Using multivariable regression models, we quantified the contributions of Vmax and environmental conditions to the variations in TC rainfall. Overall results suggest that the variation in RS according to ENSO are mainly related to Vmax, while those of RA and RV are strongly controlled by environmental conditions.

Variation of surface water extent in the great Sebkha of Oran (NW of Algeria), using Landsat data 1987–2019: Interaction of natural factors and anthropogenic impacts

The rapid and precise extraction of water information through satellite remote sensing has become a crucial technology in the study of water resources due to its ability to provide substantial and repeatable coverage instantly. This technology is particularly useful in monitoring wetlands, among other applications. It in this perceptive, this research aims to study the surface water extent (SWE) variation of the Great Sebkha of Oran (GSO). A wetland area classified as Ramsar, bordering Oran city. Extended over nearly 40,000 ha, the water extent is influenced by climatic, geological, and hydrological factors, which are typical of endorheic regions in semi-arid and arid climates. However, over the last decade, these natural effects have been overtaxed by anthropogenic impacts caused by the strong urban expansion of the city of Oran. This is particularly evident with the commissioning of the large El Kerma sewage wastewater treatment plant (WWTPK) in 2009. Located at NE edge of the GSO. The function of this plant is to treat a large proportion of the wastewater volume generated by the city of Oran. Nevertheless, for various reasons, a lag in the implantation of the various execution phases of a development project extended to the entire GSO basin has led to nearly a decade; the WWTPK has discharged partially treated wastewater directly into GSO. This had a major impact on the mode of surface water extent change of the sebkha and led to major pollution of the latter. To better understand the (SWE) dynamics, post and pre-discharges from the WWTPK in the sebkha were monitored monthly over 33 years (1987–2019). A consistent database of Landsat sensor images (TM, ETM+, and OLI) was collected and processed in the Google Earth Engine (GEE) platform to extract the SWE in the GSO, which was achieved using spectral indices: Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI1 and NDWI2), Modified Normalized Difference Water Index (MNDWI) and Dryness/Wetness index (DWI). Subsequently, the SWE, correlated with precipitation over the entire GSO watershed, was analyzed and discussed at different time steps: monthly, annual, and seasonal. Before 2009, the precipitation regime study concerning the SWE shows the complexity of the functional dynamics of the endorheic system of the GSO watershed. After 2009, the commissioning of WWTPK had disrupted the SWE variation of the GSO. The maximum average of the SWE during the 2009–2019 sub-period was 169 km2, while it was 122 km2 during the undisturbed sub-period (1987–2008). The use of remote sensing data analysis contributes effectively to this work, representing proven results to protect this sensitive natural environment. They remain necessary to help decision-makers to ensure and preserve the sustainable ecological viability of the GSO and the natural environment of wetlands of the entire Oran sublittoral furrow of Gdyel-Arzew: Daiet Morcelly, Telamine Lake, Sebkha golf Arzew.

Mesoscale Eddy Chain Structures in the Black Sea and Their Interaction with River Plumes: Numerical Modeling and Satellite Observations

The northeastern part of the cyclonic Rim Current, which encircles the entire basin of the Black Sea, is named as the Northeast Caucasian Current. It periodically approaches the coast, triggering the formation of topographic generated eddies, including long-living isolated anticyclonic eddies and short-living multiple anticyclonic eddies, which group and merge into eddy chain structures. Both types of eddies affect coastal dynamics and interact with multiple river plumes formed in the study area. This interaction determines cross- and along-shelf transport of fluvial water, enhancing the processes of self-cleaning of the coastal zone. In this study, we used a 3D low-dissipation model, DieCAST, coupled with a Lagrangian particle tracking model, and supported by analysis of satellite images, to study the generation and evolution of eddy chains and their interaction with river plumes along the Caucasian coast. Using Fourier and wavelet analyses of kinetic energy time series, we revealed that the occurrence of eddy chains ranges from 10 to 20 days, predominantly in spring-summer season in the area between the Pitsunda and Iskuria capes. During the period of eddy merging, the angular velocities of the orbiting eddies reach maximal values of 7 × 10−6 rad s−1, while after merging, the angular velocities of the resulting eddies decreased to 5 × 10−6 rad s−1. Numerical experiments with Lagrangian particle tracking showed that eddy chains effectively capture water from river plumes localized along the coast and then eject it to the open sea. This process provides an effective mechanism of cross-shelf transport of fluvial water, albeit less intense than the influence of isolated anticyclonic eddies, which are typical for autumn-winter season.

Comparison of the SCS-CN and Hydrograph Separation Method for Runoff Estimation in an Ungauged Basin: The Izmit Basin, Turkey

The separation of surface runoff and base flow is a very specific problem in water balance calculations, particularly if there is not enough measured flow data. In this study, the SCS-CN method is used to estimate the surface runoff in the ungauged Izmit Basin. The CNs are estimated using the Hydrologic Soil Groups map, based on soil data of the General Directorate of Rural Services of Turkey and land use obtained from the CORINE-2006 database for different AMCs. The surface runoff was computed using the SCS-CN method for the ungauged Izmit Basin that corresponds to 17% and 21% of the rainfall, i.e. 134 mm (for Kocaeli Meteorological Station; rainfall=804 mm) and 171 mm (for Sakarya Meteorological Station; rainfall=820 mm). According to SCS-CN method estimates, approximately 41-42% of the annual rainfall in the Izmit Basin directly contributes to the total streamflow, and 21-25% of it contributes to base flow and unmeasured infiltration. To compare the results of the SCS-CN method along with hydrograph separation method, the gauged Yuvacık Dam Sub-Basin, which is hydro-meteorologically similar to the Izmit Basin, was selected. The results showed that 16% of the rainfall in the Yuvacık Dam Sub-Basin became surface runoff. Also, it was found that about 42% of the annual rainfall in the Yuvacık Dam Sub-Basin directly contributes to the total streamflow and 23% of it contributes to the base flow and unmeasured infiltration. These results confirm that the ratio of surface runoff obtained by the hydrograph separation method in the Yuvacık Dam Sub-Basin matches with the ratio of surface runoff calculated using the SCS-CN method for the entire Izmit Basin.

Accounting of public preferences and valuation of terrestrial and aquatic ecosystem services restoration: Evidence from Northwestern China

The emphasis of current study is on the assessment of households’ willingness to pay (WTP) and preference heterogeneity for the upgradation of degraded terrestrial and aquatic ecosystem services across sub-basins of Heihe River. A sum of 1679 households were interviewed through choice experiment, and random parameter logit model is applied for welfare estimation. The estimated results signified the importance of selected terrestrial and aquatic ecological attributes. Sampled respondents of upper and middle basins placed highest WTP for reducing the emission of greenhouse gases among all other attributes and the WTP amount was 99.27 and 66.49 Yuan/Year respectively. Whereas in lower basin, improvement in landscape of farmland was highly valued, i.e., 107 Yuan/Year. In terrestrial ecosystem services the lowest WTP was recorded for Ejinaqi oasis size in all sub basins. In aquatic ecosystem services, improving water quality was the most valued attribute in all sub basins, and the corresponding WTP values are 122.81, 99.87 and 177.43 Yuan/Year in upper, middle and lower basins respectively, which ensure the significance of water quality in the entire basin. In aquatic ecosystem services the lowest WTP amount was recorded for leisure and entertainment conditions in each sub basin.

Regional analysis of the 2015–16 Lower Mekong River basin drought using NASA satellite observations

Study regionLower Mekong River Basin (LMRB) Study focusSatellite remote sensing products are widely used for monitoring droughts. Using NASA satellite sensors of precipitation (Global Measurement Mission, GPM), soil moisture (Soil Moisture Active and Passive, SMAP), and terrestrial water storage (Gravity Recovery and Climate Experiment, GRACE), this study evaluates the historical drought in the LMRB during 2015–16. SMAP soil moisture was validated against in-situ soil moisture, and GPM precipitation and SMAP soil moisture were cross-validated with streamflow observations. The spatiotemporal dynamics of soil moisture were also examined in different ranges of catchment areas. In performing the analysis, we used lagged correlations between hydrological variables and the indices of the Standardized Precipitation Index (SPI) and Standardized Streamflow Index (SSI). New hydrological insights for the regionsSpatio-temporal patterns of drought in 2015–16 were examined from the entire basin to small watersheds. A mismatch occurs when using GRACE data to study droughts in small watersheds (many of the small watersheds would be a fraction of the few 100 km2 spatial resolutions of GRACE pixel). In smaller watersheds, hydrological drought (SSI) was closely defined with SMAP soil moisture downscaled to 1 km rather than the meteorological drought index (SPI). By leveraging satellite-based observations across a range of spatial scales, this study highlights the utility of Earth observations in informing water resources and land management decisions at the regional scale.

Quantifying the impacts of hydraulic infrastructure on tropical streamflows

AbstractHydraulic infrastructures, such as reservoirs and water diversion channels, cause altered streamflow worldwide. Therefore, this study aimed to assess the coupled impacts of reservoir operations and water transfer on downstream streamflow over 42 years (1979–2020) for a tropical river in Vietnam, the Vu Gia Thu Bon (VGTB). We also quantified variations in the multi‐sub‐basin contributions to the water budget associated with hydraulic structure development. Therefore, a semi‐distributed hydrological model, SWAT (Soil and Water Assessment Tool), was developed for the entire VGTB basin considering two plausible scenarios: with a dam and without a dam. In this study, reservoirs substantially affected the streamflow during the 2011–2020 period when 12 cascading hydropower dams were constructed in the Vu Gia sub‐basins. The cascading reservoirs across the Vu Gia River reduced the annual average streamflow by 28.1% during this period, whereas their influence was augmented by 13.9% at reaches further downstream. In contrast, the local reservoir and flow diversions created on the Thu Bon River resulted in a 6.5% increase in streamflow. The upstream reservoir operation significantly increased streamflow at the midstream stations by 27.8% compared to the no‐dam period. The streamflow decreased in the dry season by 5.6% in the Vu Gia sub‐basins and increased by 61.7% in the Thu Bon sub‐basins. However, the impacts decreased in the wet season by 41.3% due to the operation of reservoirs, in which Dak Mi 4 had the most significant influence. It was found that the water diverted to the Thu Bon River was governed and reduced by the cascading hydropower dams. Therefore, the operation of 11 reservoirs has partially compensated for the lost water in the Vu Gia sub‐basins, to which the Dak Mi 4 plant has transferred 19.7 m3/s (14%). Our findings classify the impact of cascading dams and diversion structures and their interaction with climate change.

Morphometric Parameters and Geospatial Analysis for Flash Flood Susceptibility Assessment: A Case Study of Jeddah City along the Red Sea Coast, Saudi Arabia

Flash floods are one of the most common and destructive natural hazards, and recent flood events show their severe impact on Saudi Arabia. Flash floods are increasing year by year in duration and intensity, resulting in huge destructive impacts for the nation concerned. Anticipating the spatial patterns and occurrence of rainfall-induced floods is in high demand. Recent technique-based studies and their comprehensive results aid in understanding the flood potential of the drainage basins and in minimizing the risks of a threat to humans and of economic damage. Jeddah City is located at the western coast of the Red Sea in Saudi Arabia and is one of the most important coastal cities in the Arabian Kingdom. It has experienced several destructive flash flood events, particularly in 2009 and 2011, causing serious damage and significant loss of life. An analysis of the morphometric parameters using geospatial techniques provides significant insights into the hydrological response of the drainage basins to major heavy rainfall events. In this paper, two relative flood susceptibility scenarios were produced: drainage basin levels and very accurate pixel-level conditions. The morphometric comparison levels suggest that basins 1 and 7 are very high, whereas the other basins have moderate and low levels. The derived flood susceptibility map was integrated with the topographic position and wetness algorithms (TPI and TWI) through overlay processing. The integration analysis aids in realizing the relationship between the general basin morphometric characteristics and the in situ relief for producing the flood susceptibility spots over the entire basins. Thus, the method of this paper can be applied to evaluate the site-specific plan minimizing the effects of flash flood risks in similar areas.

Fish fauna of the trans-Andean Tumbes river basin in northern Peru

To update the knowledge of the ichthyofauna of the Tumbes River basin, we provide a list of species. We report 47 species of fishes, grouped into 23 families and 11 orders. Characiformes was the most diverse order with 12 species (25.5% of the total richness), followed by Carangiformes with eight species (17%). In our study, two species are newly reported from this river basin: Pseudophallus starksii (Jordan & Culver, 1895) and Evorthodus minutus Meek & Hildebrand 1928. According to salinity tolerance, the ichthyofauna is composed of 20 primary, 14 secondary, and 13 peripheral species. Despite having the highest diversity of fish on the Peruvian Pacific slope, the Tumbes river basin is one of the most polluted coastal drainages. This study compiles information on the ichthyofauna of the entire basin, increases the known diversity of freshwater fish from trans-Andean drainages in Peru, and can be used in the management and conservation of the Tumbes River.

Towards a strategy for the recovering of the Mediterranean monk seal in the Adriatic-Ionian Basin

Occasional but recurrent sightings indicate that the endangered Mediterranean monk seal is still present in most of its historical range within the Adriatic-Ionian region in the central Mediterranean Sea. However, in most of the adjacent countries, the species’ abundance and distribution are practically unknown. An actively reproducing sub-population with a minimum of 25 adult/sub-adult seals lives in the Greek central Ionian Sea. The latter can form a nucleus from which the entire Adriatic-Ionian Basin could be re-colonized if adequate conservation measures are implemented throughout the area and in a coordinated manner. We examine the historical presence in the region as a baseline for providing a benchmark for conservation. We further look into the species’ habitat availability, possibilities for a rapid population assessment and various parameters that are considered crucial for its conservation, such as the existence of Marine Protected Areas (MPAs), corridors for connectivity purposes as well as needs for raising public awareness. We recommend a series of interlinked actions within the framework of a conservation strategy the implementation of which will ensure the conditions for maintaining ecologically, demographically, and genetically viable sub-populations of this species emblematic for the entire Mediterranean Sea. To achieve this goal, a coalition of partners from this area is required in order to adopt the strategy and jointly implement the measures required.

Carbonate U-Pb Geochronology and Clumped Isotope Constraints on the Origin of Hydrothermal Dolomites: A Case Study in the Middle Permian Qixia Formation, Sichuan Basin, South China

Reservoirs in the dolomites of the Middle Permian Qixia Formation in the Sichuan Basin are currently important oil and gas exploration objects in China. However, the questions concerning the sources of the dolomitized fluids and the control factors of the Qixia hydrothermal dolomites remain unclear. In this study, the original hydrothermal dolomites (the replacement dolomites (RDs) and saddle dolomites (SDs)) from the Qixia Formation in the southwestern Sichuan Basin (the PR1 well and Baoxing section) were mainly examined using novel in situ carbonate U-Pb dating with clumped isotopes (∆47). Our results show that the U-Pb ages of the latest SDs from the PR1 well (located in the middle zone of the Emeishan large igneous province (ELIP) and distanced from the Orogenic Belt of Longmenshan) are 257.9–251.0 Ma, coincident with the period of main activity of the ELIP. Combined with the previous U-Pb dating, we propose that the high-temperature T∆47 (82.2–108.4 °C and 127.5–205.9 °C) recorded for SDs from the PR1 well and Baoxing section may have responded to ELIP activity and Longmenshan orogeny activity, respectively. In addition, in the entire southwestern Sichuan Basin, the RDs and SDs yield similar δ13C and δ18O values, indicating that the dolomites were formed by hydrothermal fluids of similar sources, with marine hydrothermal fluids being a highly possible source. Finally, this study proposes a new hydrothermal dolomite genesis model for the Qixia Formation, emphasizing that the formation of hydrothermal dolomites mainly depends on the proximity to tectonic thermal events in space and time.

Innovation, Integration Enable Success in Guyana-Suriname Basin

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper OTC 30946, “Innovation and Integration: Exploration History, ExxonMobil, and the Guyana-Suriname Basin,” by Audrey L. Varga, Matthew R. Chandler, and Worth B. Cotton, ExxonMobil, et al. The paper has not been peer reviewed. Copyright 2021 Offshore Technology Conference. Reproduced by permission. _ Exploration in the Guyana-Suriname Basin has been a decades-long endeavor, including technical challenges and a lengthy history of drilling with no offshore success before the 2015 Liza discovery. The collection of extensive seismic data has been leveraged to enable successful exploration of multiple play types across the basin. Further data collection has enabled the operator to adopt interpretation techniques that are applied across the entire basin to characterize and understand the subsurface better. Historical Context The first wells drilled in the Guyana-Suriname Basin were onshore; the Rose Hall well in Guyana in 1941 first found oil shows. Rumors of oil in the region, and hopes that the prolific hydrocarbon systems present in Venezuela extended into Guyana and Suriname, led geologists from the Standard Oil Company to conduct initial reconnaissance and seismic and geochemical studies. Despite hints—in retrospect—of a favorable basin configuration and hydrocarbon presence, the decision was made to discontinue exploration activities. Through the 1950s and early 1960s, the region saw relatively low levels of activity. In 1960, the first well was drilled offshore Guyana, and, in 1964, the first offshore well was drilled in Suriname; both were dry. In 1965, the Geological and Mining Service of Suriname found heavy oil near the present-day Calcutta Field. This led to the discovery of the Calcutta, Tambaredjo, and Weg naar Zee heavy-oil accumulations, but only a thin reservoir and heavy oil were encountered. In 1975, Esso participated in the North Coronie-1 well in Suriname. The well found oil and gas shows, confirming the presence of immature but rich source rock that was age-equivalent to the prolific La Luna source in Venezuela. A reconnaissance 2D seismic program followed, and, in 1978, Esso drilled the first deepwater well at Demerara A2-1. This well also was dry but did find high-quality, immature source rock and weak oil and gas shows. After another disappointing well at FG-1 in French Guyana in 1978, Esso ultimately relinquished its licenses but noted the presence of excellent-quality source rocks and reservoirs. The onshore Tambaredjo field, discovered in the 1960s, did not start production until 1982. All in all, before the Liza discovery, more than 300 wells were drilled in the basin, with more than 200 of these dry. Of these, all 60 offshore wells were dry. Why, then, did exploration continue? Data Evolution In the mid- to late-1990s, the Guyana deepwater acreage was completely open. The data available to the operator’s geoscientists consisted of one or two seismic lines, approximately four offshore wells, and a Suriname onshore oil sample. At that time, a major change in global coverage and quality of satellite free-air gravity data occurred with the declassification of US military data. An internal project by the operator merged the Sandwell and Smith free-air gravity grid, available in the public domain, with Getech onshore Bouguer gravity grids to create a global gravity compilation. The operator’s researchers recognized the applicability of these data as a key technology enabler to update plate tectonic models and genetic basin analysis.

Widespread Frequent Methane Emissions From the Oil and Gas Industry in the Permian Basin.

Emissions of methane (CH4) in the Permian basin (USA) have been derived for 2019 and 2020 from satellite observations of the Tropospheric Monitoring Instrument (TROPOMI) using the divergence method, in combination with a data driven method to estimate the background column densities. The resulting CH4 emission data, which have been verified using model data with known emissions, have a spatial resolution of approximately 10km. The CH4 emissions show moderate spatial correlation with the locations of oil and gas production and drilling activities in the Permian basin, as well as with emissions of nitrogen oxides (NOx). Analysis of the emission maps and time series indicates that a significant fraction of methane emissions in the Permian basin is from frequent widespread emissions sources, rather than from a few infrequent very large unplanned releases, which is important considering possible CH4 emission mitigation strategies. In addition to providing spatially resolved emissions, the divergence method also provides the total emissions of the Permian basin and its main sub-basins. The total CH4 emission of the Permian is estimated as 3.0±0.7Tgyr-1 for 2019, which agrees with other independent estimates based on TROPOMI data. For the Delaware sub-basin, it is estimated as 1.4±0.3Tgyr-1 for 2019, and for the Midland sub-basin 1.2±0.3Tgyr-1. In 2020 the emissions are 9% lower compared to 2019 in the entire Permian basin, and respectively 19% and 27% for the Delaware and Midland sub-basins.

Understanding regional groundwater flow using water-rock interaction processes and anthropic signatures in a fractured volcanic aquifer

This research evaluated the hydrochemistry of a fractured volcanic aquifer at Paraná 3 Basin, in the western region of the state of Paraná, southern Brazil. Geochemical rock data from the literature were used to describe the distinctive characteristics of the principal geological units in the area, Pitanga and Paranapanema Formations, both belonging to the Serra Geral Group. Data from x-ray diffraction were obtained to deepen the study of hydrogeochemical processes. Previous studies did not consider the differences in the lithogeochemistry of the group, in the terms contemplated in this research. In addition, the research also approaches the evaluation of the flow depth contribution in the groundwater chemistry and the analysis of hydrogeochemistry processes. For this analysis, a set of chemical data was utilized on 35 groundwater samples from water supply boreholes at Paraná 3 Basin. From shallow to deep flow, there was an increase in pH, electrical conductivity, total dissolved solids, total alkalinity and a decrease in CO2. These parameters exert the main physical-chemical groundwater controls, which are identified by changes in the major ions along the flow lines, as well as by variations in trace elements. The water-rock interaction becomes increasingly evident in the intermediate and deep flows, standing the higher alkalinity, pH, electrical conductivity, total dissolved solids (TDS) and most of the trace elements at Pitanga Formation. Pitanga Formation presents higher medians of alkalinity (95.5 mg.L-1), electrical conductivity (225 μS.cm-1) and TDS (140.0 mg.L-1) than Paranapanema Formation (57.0 mg.L-1; 130 μS.cm-1 and 90.0 mg.L-1, respectively). Furthermore, the pH distribution shows greater values starting at the 60% percentile in Pitanga Formation (8.24), compared to Paranapanema (8.10). Despite such differences, it was not possible to distinguish the geological units with the hydrochemical characterization, probably because both units are mainly represented by rocks of basic composition, with a similar mineralogical basis. The shallow hydrogeochemical processes are characterized by the weathering of Fe–Mg silicates and plagioclase, changing to a predominance of ion exchange in deeper flows. Calcite precipitation is a secondary process, associated with calcium consumption towards deeper flows. Anthropic influences are mainly observed with more elevated concentrations of NO3-, PO43-, Cl- and K+, occurring in the entire basin, and they are strongly evidenced by the correlation between Cl- and NO3- in most samples.

A multiscale ocean modelling system for the central Arabian/Persian Gulf: From regional to structure scale circulation patterns

The Arabian/Persian Gulf (hereafter, the “Gulf”) is one the busiest and fastest changing sea in the World. Its circulation is primarily driven by the surface water inflow from the Sea of Oman and density-driven and wind-driven flows within the Gulf. The regional circulation in its central part, particularly around Qatar, could not be explored because of unavailability of measured current data and the coarse resolution opted for the entire Gulf modelling. In the present study, we developed a high-resolution ocean modelling system of the entire Gulf with a particular focus on Qatar coastal waters. The model uses an unstructured mesh with different resolutions ranging from ∼5 km in the open ocean to ∼150 m along the coast of Qatar and less than 40 m around artificial structures. The model results have been validated with in situ data collected off Qatar. It allows seamless simulations of hydrodynamic processes from the entire basin scale down to the scale of coastal structures. The study identifies seasonal variability in currents and eddies in the central part of the Gulf. It also suggests the existence of four prominent anticyclonic eddies in the Gulf of Salwa, south of Bahrain. At the structure scale, the flow is mostly tidally driven and can be intensified beyond 1 m/s through narrow passages such as between breakwaters or within artificial waterways. By explicitly representing the effect of ocean sprawl on the coastal circulation, our model has the potential to greatly improve the environmental impact assessment of coastal developments in the Gulf area.

Spatial attribution of declining Colorado River streamflow under future warming

Studies of climate change impacts in the Colorado River Basin have focused on the Upper Basin, finding that warming has exacerbated streamflow declines since 2000. Presently, it is unclear if the predicted high degree of interannual precipitation variability across the basin could overwhelm impacts of future warming and how this might vary in space. To address this, we employed an updated Variable Infiltration Capacity model framework to generate streamflow projections across the entire basin. Meteorological data were drawn from downscaled historical and future climate projections of eight climate models that best represent climatology. Results showed a high confidence of Far-Future (2066–2095) mean annual streamflow declines (relative to the Baseline, 1976–2005) at the Upper Basin, Lower Basin, and basin-wide scales (ensemble median trends of −5 % to −25 %). Streamflow declines were attributed to warming that diminished snowfall and melt during April to September and year-round increased soil evaporation from the Upper Basin, and overall precipitation declines in the Lower Basin. Widespread reductions in annual runoff and baseflow efficiencies indicated that precipitation increases did not offset the noted warming effects. Spatial coherence tests indicated that streamflow correlations among subbasins remained relatively constant in the future scenarios, though correlations with the Green River increased. This spatial attribution analysis is providing actionable information for water management in the Colorado River Basin under current and future conditions.

Morphometric analysis of shel dedumal watershed using remote sensing remote sensing and GIS

Morphometric analysis is the measurements and mathematical analysis of the land surface configuration, shape and dimension of the landforms. The efficiency of the drainage network is very important for understanding the processes of landform formation, soil physical properties and erosion characteristics. The present study is focused on the evaluation of morphometric parameters for conversation of soil and water on delineated in the basin. Furthermore, morphometric analysis of watershed using geospatial data and GIS techniques and slope analysis were also utilized to propose the suitable soil and water conservation measures in the basin. The results obtained in the analysis revealed that the Shel Dedumal basin tributaries is an 5th order drainage basin which describe that the texture is homogeneous or homogeneity still exist and lack of structural control in soil strata. The relief ratio (R h ), the elevation difference (R h or H) and circularity ratio (R c ) was found to be 10.73, 222.0 and 0.42, respectively which represents the basin having moderate relief and gentle to moderately high slope. Some areas of the basin are characterized by variation in Lithology and topography. The mean values of bifurcation ratio (R b) observed as 4.52 and circularity ratio (R c ) observed as 0.42 of the entire basins shows a moderate but not strong structural control or structural disturbances. An extreme high value of ruggedness number (R n ) observed as 11.83 which indicate the structural complexity of the terrain. The Moderate drainage density (D d ) and circularity ratio (R c ) was observed as 2.63 and 0.42, respectively which indicates the basin is highly permeable subsoil and vegetative cover. The form factor (F f ), the elongation ratio (R e ) and circularity ratio (R c ) was observed as 0.39, 0.71 and 0.42 respectively which is indicating elongated basin with lower / flatter peak flows of longer duration than the average and also the elongation ratio (R e ) values indicating moderate to slightly steep ground slope in basin which is indicating possibility for soil erosion and other soil and water conservation works.

Impact of Dense Water Formation on the Transfer of Particles and Trace Metals from the Coast to the Deep in the Northwestern Mediterranean

This study aimed to describe the interannual variability of dense shelf water cascading and open ocean convection in the Gulf of Lions (NW Mediterranean) based on long-term temperature and current records and its impact on particle fluxes and associated metals. These observations highlight the predominant role of the rare intense events of dense shelf water cascading (1999/2000, 2005/2006, 2012/2013) in the basinward export of particles, which are mainly brought by rivers. Measurements of particulate trace metals in 2012 indicate that the monitored intense cascading event may be responsible for a significant fraction (~15%) of the annual input to the shelf. To this first process is added the effect of somehow more recurrent deep convection events (2005, 2009–2013) that remobilize the deep sediments, receptacle of coastal inputs, and disperse them rapidly at the scale of the northern Mediterranean basin, and gradually over the entire western basin. Coastal and oceanic dense water formations are key physical processes in the Mediterranean margins, whose reduction in intensity and recurrence has already been observed and also anticipate in climate scenarios that will likely change the dispersion pathways of chemical particles in this region.