Extreme Western Research Articles

Geohistorical and geoarchaeological evidence of seafaring in the Caspian Sea: Lessons from the past to draw the future

The Caspian Sea, the Earth’s largest lake, straddles the continents of Asia and Europe and has historically served as both a barrier and a conduit for human development. The maritime activities within the Caspian Sea have been profoundly shaped by its dynamic sea-level fluctuations, coastal geomorphology, and climatic conditions as well as the socioeconomic and geopolitical situation. Despite a rich history of navigation and numerous related monuments, there has been a scarcity of research on marine archaeological evidence assessing the influence of historical environmental and socioeconomic shifts on the development of maritime activities in the Caspian Sea. In this study, we employed geohistorical, geoarchaeological, and archaeological methodologies to unearth evidence of maritime activities along the Caspian’s southern coast. We investigated 12 archaeological sites and historical shipwrecks, unveiling their maritime historical and archaeological significance. Our findings indicate that there are two distinct patterns of port migration. The transverse migration of ports has predominantly occurred in reaction to swift changes in Caspian Sea level. Additionally, we have identified a long-term migration of ports from the eastern to the western extremities of the southern coast, driven by geopolitical, socioeconomic, and environmental transformations. Drawing on historical and archaeological insights, and considering contemporary global initiatives aimed at forging east–west and north–south connections through the Caspian Sea, as well as the ongoing climatic changes affecting the Caspian Sea level, we anticipate a forthcoming wave of port migrations along its coastlines.

Novel Model of Kidney-Cardiovascular-Metabolic Injuries by Unilateral Nephrectomy and an Extreme Western Diet: Beneficial Effects by a Natural Food Additive (FLX)

Novel Model of Kidney-Cardiovascular-Metabolic Injuries by Unilateral Nephrectomy and an Extreme Western Diet: Beneficial Effects by a Natural Food Additive (FLX)

Gastrointestinal nematodes in Cuniculus paca (Linnaeus, 1766) from hunting fauna in the Western Amazonian region

Cuniculus paca, commonly known as the paca, is a rodent of the Cuniculidae family that is widely distributed throughout the Americas, including all Brazilian territories, and is abundant in the Amazon region. It is one of the most hunted species and faces significant predation in the extreme western Amazon region of Brazil because it constitutes a staple in the diet of local communities, for subsistence and commercial purposes. Understanding the helminthic fauna of these animals is of paramount importance, given that some nematodes have zoonotic potential and may pose risks to consumer health. This study aimed to contribute to the records of the nemtodes of this highly consumed species in the Amazon region, highlighting the occurrence of gastrointestinal parasites in free-living pacas intended for human subsistence consumption. The study was conducted in the Paranã da Floresta community, located in the municipality of Guajará, Amazonas from 2022 to 2023. The community members hunted this rodent for consumption and voluntarily provided the viscera for analysis. Nematodes were extracted from each organ. The organs were opened, and the contents were processed using a sieve (0.15 mm) and subsequently evaluated separately. In total, 10,157 nematodes were found in the 14 pacas. Based on morphological analyses, the nematodes were identified as Heligmostrongylus sedecimradiatus (n = 10,068), Trichuris sp. (n = 85), and Physaloptera sp. (n = 4). This study provides insights into the nematodes diversity of free-living pacas in the extreme Western Amazon region, emphasizing the importance of sanitary surveillance and public awareness of the risks associated with bushmeat consumption.

Assessing Potential Evapotranspiration Methods in Future Drought Projections across Canada

abstract Recently, concerns have arisen as to whether temperature-based proxy methods used to estimate potential evapotranspiration (PET) are reliable when examining future drought severity, especially in the context of a warmer climate. The objective of this study was to assess the effect of different PET approaches, focusing on proxies for radiation and humidity, on future Standardized Precipitation Evapotranspiration Index (SPEI) calculations across Canada. Using output from 22 CMIP6 global climate models (GCMs), seasonal and annual SPEI comparisons were carried out between the physically-based Penman-Monteith (PM) method and two approaches that incorporate temperature proxies to calculate radiation and/or humidity. These included the temperature-based Hargreaves (HG) approach and a PM method with derived humidity (PM-m). Results revealed that although the general patterns of SPEI projections across Canada were consistent among the methods, notable spatial and temporal differences were apparent. Specifically, both median and extreme SPEI projections based on the two temperature proxy methods revealed less annual and summer drying in much of central, eastern, and northern regions of Canada when compared to the physically based SPEI-PM. In extreme western regions (British Columbia, Yukon) these two methods, particularly HG, projected drier conditions. Differences of using temperature derived radiation and humidity were also most apparent in spring (and to a lesser degree, autumn), where the HG approach overestimated spring drying (and autumn wetting) over large regions of the country. Overall, differences tended to be more pronounced for the fully temperature-based HG approach during all periods considered. Results from this study strongly suggest that when possible, a physically-based approach be used when estimating PET to assess future drought projections. If a temperature proxy is used, the differences to a physically-based method should be understood and resultant implications be evaluated.

Structural geometry and geomorphic evolution of the Trans Indus Manzai Ranges, Western Himalayas, Pakistan

At the leading edge of fold-thrust belts, structural deformation can either be accommodated by thick-skinned faulting, and development of structural wedges near the mountain fronts, or by foreland propagation into the basins along the detachment, forming thin-skinned structures. Manzai Ranges at the western extremity of the Trans Indus Ranges were chosen as a case study to describe the structural deformation accommodated in the foreland basin and to study the folded mountain front. These ranges also provide an opportunity to compare along-strike structural variations of the Himalayan frontal thrust system. Both surface (field structural measurements and digital elevation model) and subsurface (2D seismic reflection and well) data were integrated to document different structural styles and their corresponding geomorphic expressions. Based on seismic reflection profiles, the results of structural interpretations constrain westward dipping basement (2.5o) at a depth of ∼10 km in the foreland, which dips deeper in the hinterland. In addition, our interpretation shows a basin-wide Eocene-Miocene unconformity that marks the Himalayan orogenic events. The structural geometry of the frontal Surqamar anticline is quantitatively characterized to be detachment fold, while Jandola, Kundi and Manzai anticlines demonstrate staircase geometry and characterized as fault-bend folds. The kinematics of development varies along-strike in the Manzai Ranges as displacement transfers along the detachment from typical fault-bend folding in the Manzai anticline to detachment folding in the Surqamar anticline, forming thin-skinned structures. The results of this study highlight the structural styles and their evolution in the context of active Himalayan tectonics.

Tsunami or storm? A high-level coastal boulder field on the southern tip of Eyre Peninsula, South Australia

A high-level coastal boulder field at Whalers Way, southern Eyre Peninsula, South Australia, occurs at elevations of 20–30 m above present sea-level on a gently seaward-sloping, karst-weathered calcrete-capped structural bench, formed on the Upper Pleistocene Bridgewater Formation and underlying Carnot Gneisses (Archean–Paleoproterozoic Sleaford Complex). More than 1000 ex situ boulders, cobbles and pebbles of gneiss and mafic igneous rocks, as well as fragments of calcrete, occur within the boulder field and cover an area >6000 m2. All the crystalline rock clasts are derived locally from bedrock outcrops along the adjacent coastline, where metasedimentary granulite-facies of the Carnot Gneisses crop out along shore platforms and their backing cliffs, close to present sea-level. The boulder field is younger than Marine Isotope Sub-Stage 5a (MIS 5a; ca 80 ka) based on amino acid racemisation ‘whole-rock’ analyses of calcarenite of the Bridgewater Formation, which forms the calcrete bench on which the boulder field rests. The boulder field wraps around the western extremity of cliff-top dunes dated at 18–17 ka by optically stimulated luminescence, implying that the boulder deposit post-dates the formation of the cliff-top dunes. Given that the clasts in the boulder field show minimal weathering rinds, sea-level during the Last Glacial Maximum was some 125 m lower than present and that between 80 and 7 ka ago, sea-level never attained present levels within the region, emplacement of the boulder field by a high-energy wave event in the Holocene highstand, following the 7000 years BP culmination of post-Glacial sea-level rise, is suggested. Storm waves, rather than a tsunami, most likely explain the emplacement of the boulder field.

Systematics of the Thirteen-scaled Green Snake Philothamnus carinatus (Squamata: Colubridae), with the description of a cryptic new species from Central and East Africa

ABSTRACT Recent molecular phylogenies of African Green Snakes suggested the geographically widespread species Philothamnus carinatus includes at least two distinct lineages. We utilised an integrative taxonomic approach with morphological and genetic data to reconcile the taxonomic status of these cryptic lineages, including the recently described taxon P. brunneus from West Africa. We sequenced three mitochondrial (16S, cyt b and ND4) and two nuclear (c-mos and RAG1) genes from several Central African populations of P. carinatus and combined our data with other closely related species to infer a maximum likelihood phylogenetic tree with IQ-TREE. Our results are consistent with previous studies that showed P. cf. carinatus populations from Democratic Republic of the Congo (DRC) represent a cryptic lineage that is distinct from P. carinatus sensu stricto in Cameroon, Central African Republic, Equatorial Guinea (including Bioko Island), Gabon, eastern Nigeria, Republic of the Congo, and extreme western DRC. In our preferred tree, P. brunneus (limited to 16S molecular data) was recovered as a relatively long branch in a moderately supported clade with P. carinatus sensu stricto, whereas P. cf. carinatus populations from northern Angola, most of DRC, and East Africa (Burundi, Kenya, Rwanda, Tanzania and Uganda) were described as a new species. A possible hybrid population between south-eastern Cameroon and north-western DRC is consistent with an increasing body of evidence suggesting the Ubangi River might represent a hybrid zone area.

Modern Sedimentation Patterns in Lake Issyk Kul (Kyrgyzstan), Derived From Surface Sediment and Inlet Stream Samples

AbstractThis study provides a descriptive characterization of the modern sedimentary processes in Lake Issyk Kul, Kyrgyzstan, important for the selection of a suitable coring or deep‐drilling site, interpretation of future core data and applicability of proxies. The quasi‐equidistant sampling grid of 66 sediment surface samples covers the entirety of the lake basin and is complemented by 10 samples from the major inflows. The methodological approach includes geochemical, granulometric, lipid biomarker, diatom, and statistical analyses. The quantitative and qualitative changes in sediment composition yield information on its generic origin and prevailing transport and depositional environments. The composition of the surface sediments in Issyk Kul is highly heterogenous. Nearshore deposition is mainly controlled by wave action and by fluvial sediment supply with highest quantities of detrital input coming from the high‐energetic, eastern tributaries. Sediments in the deep central basin are mainly produced in situ and dominated by authigenic calcite. Biogenic accumulation is overall low, except for the western extremity of the lake, where the nearshore, shallow‐water, and low‐energetic environment favors aquatic productivity and subsequent preservation of organic material and diatoms. Redeposition of sediments is a dominant process along the slopes across the southern and western basin floor, where run‐out distances of mass movement deposits are up to 5 km. Directional sediment transport by lake currents appears to be less important, except for the transport of very fine‐grained organic matter. Biomarker‐inferred temperature reconstructions suggest lake surface temperatures of ∼15°C in the western littoral zone and in Tyup Bay and a decrease to ∼13°C basinward.

Emplacement of a lamprophyric sheet swarm under ductile transpression in continental crust. Insights from a Variscan magmatic complex in the West Armorican belt, Western France

We present structural data from a Variscan magmatic complex of dominantly lamprophyric (kersantite) and associated felsic (microgranodiorite) sheets - the West Armorican swarm (WAS) - injected into Paleozoic metasedimentary series at the western extremity of a transpressional system in the Armorican belt, Western France. The comparative structural analysis of nearly 100 individual intrusive sheets and their host-rocks demonstrates that the WAS complex is a syntectonic magmatic structure which intruded during the onset of regional shortening via successive pulses alternating with three strain episodes (D1-D2-D3). The moderate/high dipping attitude of a great majority of intrusions, along with their prominent orientation parallel to the regional cleavage (S1), i.e. orthogonal to the direction of shortening, challenge theoretical predictions about magma-filled fractures in contractional settings. These apparently atypical features are reconciled in a kinematic model which emphasizes the influence of both host-rock planar anisotropies (S1 cleavage and D3 shear patterns) and structural inheritance on magma pathways, and instead hypothesizes the negligible role of the ambient stress field. Comparisons are attempted with syncollisional lamprophyre systems present in the European Variscides, and more especially in the SE Bohemian massif.

Distribution of the White-backed Woodpecker Dendrocopos leucotos lilfordi in the southern Pyrenees

We have compiled the information available for the White-Backed Woodpecker (Dendrocopos leucotos lilfordi) on the south-facing slopes of the Pyrenees since its detection in 1968 until 2016 and we have added the results of specific censuses carried out between 2017 and 2021 and the results of the GPS marking of reproductive specimens, both within the known range, as in other beech forests beyond its borders. An expansion towards the West and North has been verified. The nests are always located in F. sylvatica, except in the extreme western territories where they use Q. rubra too. The breeders in the traditional range are always individuals of more than two years old (euring 6), although a number of breeding juveniles have appeared in the extreme west (euring 5). Beech occupies more than 70% of the surface of all the territories, but this percentage is significantly lower in the newly detected territories than in those within the traditional distribution area. These latest results suggest that the expansion process is relatively recent and that it may still be in progress. The role of forest management in efforts to enable the expansion of this species to other beech forests in which it has not yet been detected is discussed.

An Assessment of the Lancaster Sound Polynya Using Satellite Data 1979 to 2022

Situated between Devon Island and Baffin Island, Lancaster Sound is part of Tallurutiup Imanga, which is in the process of becoming the largest marine conservation area in Canada. The cultural and ecological significance of the region is due, in part, to a recurring polynya in Lancaster Sound. The polynya is demarcated by an ice arch that generally forms in mid-winter and collapses in late spring or early summer. Advanced Very High Resolution imagery from 1979 to 2022 was analyzed to determine the position, formation and collapse of the Lancaster Sound ice arch. The location of the ice arch demonstrates high interannual variability, with 512 km between the eastern and western extremes, resulting in a polynya area that can fluctuate between 6000 km2 and 40,000 km2. The timing of the seasonal ice arch formation and collapse has implications with respect to ice transport through Lancaster Sound and the navigability of the Northwest Passage. The date of both the formation and collapse of the ice arch is variable from season to season, with the formation observed between November and April and collapse usually occurring in June or July. A linear trend from 1979 to 2022 indicates that seasonal ice arch duration has declined from 150 to 102 days. The reduction in ice arch duration is a result of earlier collapse dates over the study period and later formation dates, particularly from 1979 to 2000. Lancaster Sound normally freezes west to east each season until the ice arch is established, but there is no statistical relationship between the ice arch location and duration. Satellite surface temperature mapping of the region indicates that the polynya is characterized by sub-resolution leads during winter.

Avalanche Hazards Around Kedarnath Temple, Mandakini River Valley, Uttarakhand – A Case Study

Abstract The Shri Kedarnath town is located in the western extremity of the Central Himalaya (30°44'6.7" N; 79°04'1"E) in the Mandakini River valley. This has a total catchment area of ~67 km2 (up to Rambara), out of which 23% area is covered by glaciers. In September 2022, avalanches were observed repeatedly in the mountains to the north of Kedarnath town. Based on aerial survey and ground observations of the area around Kedarnath, we found that the avalanches initiated ~6 km (Aerial distance) uphill of the Kedarnath Temple from the peaks of the Mahalaya Parvat (5970 m asl) of the Companion Glacier adjacent to the Chorabari Glacier. The Companion Glacier does not have a well-defined accumulation zone but receives accumulation mostly from the avalanches. The run-out and deposition zones of the avalanches are located ~5 km uphill of the Kedarnath Temple. The avalanche activity thus poses no threat to the Kedarnath Temple and township. In addition, fifteen avalanche sites (A1-A15) have been identified based on slope morphology, grass clearing, the presence of snow drifts, and debris cones in the area. We observed that the Temple of Shri Kedarnath Complex is located at a reasonably safe place as far as avalanche hazards are concerned.

Analysis of the Qur’anic Concepts of Mashriq (East), Maghreb(West), Mashriqain (Two Easts), Maghribain (Two Wests), Mashariq (Several Easts) and Maghreb(Several Wests):Observations in Quetta, Pakistan

In the current era,various scientific facts revealed by the Holy Qur’an have been scientifically tested and acknowledged by the modern scientists. Scientific knowledge of Earth and related sciences confirms and support the concepts given in the relevant verses of the Qur’an. For example, the Qur’an contains verses that reveal the concepts of Mashriq(east), Maghrib(west), Mashriqain (two easts), Maghribain(two wests), Mashariq(several easts) and Magharib(several wests). This paper pinpoints and put forward scientific analysis of these concepts of the Qur’an, compares and summarizes the pre-existing conventional tafaseer(explanations) with the modern scientific judgments and deliberates on their undisputable integrity. We analyzed these concepts, using scientific methodology, on a fixed location (x,y,z= 67.002, 30.1853, 1684 m) in Quetta, Pakistan. It was observed that the positions and timing of the sunrise and sunset change daily by shifting gradually from their winter to summer extremes and vice versa in a systematicand predictable manner. This leads to a conclusion that the Qur’anic words Mashriq(east) and Maghrib(west) refers to the spans of horizons between the eastern and western extremes of the sun rises and sets. The words Mashriqain(two easts) and Maghribain(two wests) refer to the two extremes, i.e.,northern and southern positions of sunrise and sunset on the eastern and western horizons, on 22ndJune (in summer) and 22ndDecember (in winter), respectively. The words Mashariq(many easts) and Magharib(many wests) simply refer to the numerous positions of the daily sunrise and sunset on the eastern and western horizons. These results are supported by relevant verses and notions of the Qur’an that have been further explained in various tafaseer, with reference to the explanations of Ib-e-Abbas (RAA) and Akrama (RAA).

Preliminary Movement and Distribution Model for Chihuahuan Green Toads, Anaxyrus debilis, in Western Kansas

The Chihuahuan Green Toad (CGT) is a small arid-adapted toad native to extreme western Kansas. Since its listing as a Kansas Threatened Species in 1987, there has been a lack of focused research on the extent and health of the population within its Kansas range. The objective of my research has been to locate and track CGT in western Kansas in an effort to create a comprehensive life history account within the state. ARDs and manual surveys were conducted from the end of May 2022 to the end of July 2022. Due to severe drought in Logan and Wallace counties during the summer research season, few CGT were observed with little insight gained into their behaviors and movement. Preliminary analysis of observation records from my research season may elucidate behavioral trends for similar arid-adapted anurans. This presentation will cover the methods, materials, preliminary results, and implications from my research.

Zipf rank analysis highlights the exploration potential for Lithium-Caesium-Tantalum -type pegmatites in the Northern Cape, South Africa

Exploration activities for mineralised Lithium-Caesium-Tantalum (LCT) pegmatites in the metalliferous Orange River pegmatite belt (southern Africa) are hampered by a dearth of any reasonable estimates of the mineral province's residual metal endowment or of its prospectivity. To mitigate this, Zipf rank analysis has been used to estimate the likelihood of pegmatites occurring below Quaternary cover sediments which veneer extensive tracts of this mineral province. The Zipf rank analyses focused on the western extremity of the pegmatite belt near Vioolsdrif where historical mining activities have exploited several pegmatite bodies including the world-class Li–Bi–Be–Cs–Ta-mineralised Noumas 1 pegmatite. Zipf rank analyses were conducted on the surface exposures of both a comprehensive dataset of mineralised- and unmineralised pegmatites (N = 159), and on a subset which comprised only the mineralised pegmatites (N = 23). Results from the latter analysis indicate that up 11 500 m2 (or ∼11%) of mineralised pegmatite surface exposure remains to be found within the confines of the defined study area. Because our Zipf analyses considered surface exposure at the present day erosional level of the Meso-proterozoic basement rocks, we suggest this residual endowment is hidden beneath the unconsolidated cover sediments. This novel application of Zipf rank analysis to pegmatite surface exposure thus highlights the prospectivity of the Orange River pegmatite belt for several of earth's critical raw materials.

A new species of the Callophrys rubi (Linnaeus, 1758) group from Afghanistan (Lepidoptera, Lycaenidae)

A new species of the Callophrys rubi (Linnaeus, 1758) species group, C. hindukushica sp. n., is described from western extremities of the Hindu Kush range in central Afghanistan. The new species differs from the other members of the C. rubi group known from the Iranian Highland, namely C. naderii ten Hagen, 2008 from southeast Iran and C. rubi martinae ten Hagen, 2012 from northeast Iran and south Turkmenistan, in the light green colouration, greenish fringe lacking brown bordering, shape and size of the male androconia and details of the male and female genitalia. http://www.zoobank.org/urn:lsid:zoobank.org:pub:AB79DCE2-CEFE-4FDF-91F9-52EF46BA5CD2

Geoheritage and geodiversity elements of the SW Pacific: A conceptual framework

The Soutwest (SW) Pacific is an expansive oceanic region with many of its islands difficult to access and relatively unexplored in a geoheritage context. Here we provide a potential framework for systematically assessing geoheritage values of the SW Pacific and creating a holistic and multi-value inventory. We outline the use of digital terrain models as landform classification tools, and other newly available spatial data. While New Zealand is scientifically and culturally recognised as part of the SW Pacific, due to its large landmass and significant scientific data already available, here we excluded it from our analysis. Rather, the aim of our ongoing research is to provide the first comprehensive overview of the geoheritage potential and unique characteristics of small island nations of the SW Pacific. Only those islands were included in this study where geoheritage research has been initiated and include islands reflecting a good spectrum of geodiversity such as Vanuatu (Ambrym, Ambae, Lopevi, Kuwae group, Tanna), Tonga (Tongatapu, Tofua), and Samoa (Savai’i and Upolu). In a geotectonic context the SW Pacific sits on the western extremity of the large Pacific plate, resulting in a broad array of geotectonic situations where convergent plate boundary processes govern the broad geological evolution and geomorphological processes seen on the islands of our study area. Volcanism associated with plate boundaries is one of the most characteristic and recognisable geological processes linked with the region in the public perception of the area. Volcanism is associated with arc-type geosystems forming complex and compound polygenetic volcanism which offers unique geological-geomorphological elements shaping geodiversity of the region. In addition, these volcanic processes have shaped human communities since the earliest days of their establishment. The interaction of Polynesian societies with volcanism provides a unique geocultural perspective based on accumulated oral traditions, forming the basis of cultural practices that remain part of everyday life into the 21st century.

An anomalous warm-season trans-Pacific atmospheric river linked to the 2021 western North America heatwave

Atmospheric rivers are long and narrow bands of enhanced water vapour transport concentrated in the lower troposphere. Many studies have documented the important role of cold-season atmospheric rivers in producing heavy precipitation and extreme flooding events. Relatively little research has been conducted on the warm-season atmospheric rivers and their impacts on heatwave events. Here we show an anomalous warm-season atmospheric river moving across the North Pacific and its interaction with the extreme western North American heatwave in late June 2021. This system transported moisture and heat energy from Southeast Asia to the northeast Pacific. Its landfall over Southeast Alaska resulted in substantial spillover of moisture and sensible heat beyond the Pacific Coast Ranges. We provide evidence indicating that the sensible heat flux convergence and the short-lived greenhouse effect of the trapped moisture could form a positive feedback mechanism leading to the northward expansion of the heatwave event across western Canada.

An integrated assessment approach for fossil groundwater quality and crop water requirements in the El-Kharga Oasis, Western Desert, Egypt

Study regionThe El-Kharga Oasis in the Western Desert of Egypt is selected as the study area due to its hyberarid climate condition and water scarcity. In this region, the fossil groundwater is the main water source; therefore, preserving groundwater quality and quantity is mandatory. Study focusThis study evaluated groundwater suitability for irrigation purposes and assessed the water requirements of cultivated crops to optimize the water supply in hyperarid climate regions. In total, 79 deep groundwater samples were hydrochemically tested to determine the suitability for irrigation by assessing the key water quality parameters. Spatial distribution maps of all chemical parameters, such as pH, EC, SAR, RSC, SSP, TDS, total hardness, Na+, K+, Ca++, Mg++, Fe, Mn, Cl-, and SO4—, were developed. The FAO CROPWAT 8.0 model, based on the Penman–Monteith equation, was used to forecast agricultural water requirements for three years, 2010, 2011, and 2012. New hydrological insights for the regionThe groundwater had medium salinity and low sodium in 84% of the cases. In comparison, high salinity was found in 16% of the samples, indicating that groundwater can be used for many soil types with a low risk of exchangeable sodium. Except for 15 of the 79 wells, all groundwater samples had chloride concentrations less than 100 mg/l. The sulfate ion distribution map showed a low sulfate ion content in the extreme western south. The total annual irrigation water requirements of all crops for 2010, 2011 and 2012 were 199.4, 215.1, and 231.7 million m3/year, respectively, reflecting a gradual increase of approximately 16.57 million m3/total area/year due to the expansion of the cultivated area. The analysis showed that modern irrigation systems reduced the amount of irrigation water by 32% and increased the cultivated area by 45% compared to conventional irrigation methods. Severe groundwater depletion occurred during the dry season from March to July, which exacerbated the water stress in the study region. The results confirmed that the region is under water stress. Accordingly, water conservation is urgently recommended.

Assessing the impacts of climate change on climatic extremes in the Congo River Basin

The Congo River Basin, located in central Africa, is the second-largest river basin in the world, after the Amazon. It has a drainage area of approximately 3.7 M km2 and is home to 75 million people. A significant part of the population is exposed to recurrent floods and droughts, and climate change is likely to worsen these events. Climate change studies of the Congo River basin have so far focused on annual and seasonal precipitation, but little attention was paid to extreme climatic events. This study aims to assess future changes in rainfall-induced flash floods and drought regimes in the Congo basin from the present day to 2100, using four selected extreme climatic indices as proxies to these two natural disasters. The indices are the total annual precipitation (PCPTOT), the number of days where rainfall is above 20 mm (PCP20), the standardized precipitation index (SPI), and the standardized precipitation-evapotranspiration index (SPEI). The indices were calculated with the statistically downscaled output of eleven Regional Climate Models (RCMs) from the Coordinated Downscaling Experiment (CORDEX-AFRICA) under two Representative Concentration Pathways: RCP 8.5 (high emissions scenario) and RCP 4.5 (moderate emissions scenario). Precipitation and temperature simulated by the RCMs were statistically downscaled using quantile mapping, while wind speed, solar radiation, and relative humidity were projected using K-nearest neighbor downscaling. The evolution of the indices was then assessed between the reference period (1976–2005) and three future periods (2011–2040, 2041–2070, and 2071–2100). Multimodel average results suggest that (i) independently of the scenario and period, PCPTOT and SPI will increase in the north, east, and western extremities of the basin and decrease in the basin’s center. (ii) The maximum increase (+ 24%) and decrease (− 6%) in PCPTOT were both projected under RCP 8.5 in the 2071–2100 period. (iii) PCP20 will increase independently of the period and scenario. Under RCP 8.5, in the 2071–2100 period, PCP20 will increase by 94% on average over the whole watershed. (iv) The SPEI results suggest that in all periods and scenarios, the rise in evapotranspiration due to higher temperatures will offset annual precipitation increases in the north, east, and western extremities of the basin. Increased evaporation will exacerbate the decrease in annual precipitation in the center, leading to increased drought frequency in the entire basin.