Dominant Water Source Research Articles

Water uptake patterns and rooting depths of Tamarix ramosissima in the coppice dunes of the Gurbantünggüt Desert, China: a stable isotope analysis.

Tamarix ramosissima has an important role in stabilizing sand dunes in desert ecosystems. Understanding the water use strategies of T. ramosissima is essential to understand its adaptations on coppice dunes. We utilized the stable isotopes δ2H and δ18O in soil water, groundwater, and xylem water to identify monthly differences in water sources. Additionally. we explored rooting depth using 2H2O as an artificial tracer. In May, T. ramosissima derived 75% of its water from shallow and middle soil layers. In July, it absorbed 90% water from middle and deep soil layers. In August and September, it acquired approximately 80% of its water from deep soil layers. The labelling using 2H as an artificial tracer indicated that the root system of T. ramosissima could reach depths >500 cm in the coppice dunes. 2H absorption was observed at depths of 100, 200, 300 and 400 cm. Soil water is the dominant water source for T. ramosissima in the coppice dunes because groundwater is at depths >30 m. The flexible water-use strategies of T. ramosissima enable it to effectively utilize different available water sources to adapt to the arid environment. These findings improve our understanding of water uptake patterns and drought adaptation strategies of T. ramosissima in the coppice dunes of desert ecosystems.

Behavioural faecal exposure pathways in a nomadic lifestyle :

Background: Water, sanitation and hygiene (WASH) is the cornerstone for health and growth at all stages of life in maintain health and increase in life span. Poor sanitation has led to disease increase in microorganisms such as Escherichia coli. Sanitation is influenced in a community by factors such as perception, behavioral practices such as open defecation and disposal of these waste. This study aimed to identify behavioral faecal exposure pathways in the nomadic community of Turbi ward. Methods: Mixed method approach using qualitative and quantitative research methods was applied in this study to assess exposure pathways and related behavior among the nomadic community of Turbi ward. Thematic data analysis was used to analyze data generated from behavioural observations. Data was presented using graphs and pie charts. Results: A total of 100 households were sampled and about 68% (n=100) of population use surface water for domestic. Turbi manyatta had the highest with 30% (n=100), followed by Kambi Nyoka at 16%(n=100) and the least was Shurr manyatta at 2% (n=100). Surface water was the dominant source of water for these community. About 76% (n=100) of the households did not treat their water before use for domestic purposes and due to scarcity of water the community store water in jerricans for more than one week. About 87% of the residents reported not washing hands before milking animals. Open defecation was the predominant method of waste disposal among the five selected Manyattas, accounting for 95% (n= 100). There was significant relationship between practicing open defecation and using surface water without treatment for domestic purpose at p-value 0.032 (95% CI), using Wilcoxon Signed-Rank test. Conclusion: The study revealed that the study community’s behavioral practices exposes them to faecal exposure due to habitual practice of open defecation, throwing waste to the bush, open burning, drinking untreated surface water and not washing hands before milking animals. There is need for advocacy on social behavior change, and strategies on health promotion targeting Water, Sanitation and Hygiene (WASH).

Effects of groundwater level decline on soil‐vegetation system in semiarid grassland influenced by coal mining

AbstractAlthough it is well known that groundwater significantly influences the plant communities, there have been few studies on how the soil and plant communities respond to a rapid decline of groundwater in a short time affected by coal mining. This paper focuses on the examination of changes in groundwater depth before and after coal mining and the soil‐vegetation response in a typical semi‐arid grassland coal mine area of Hulunbuir Steppe, Northeastern China. The IsoSource model, based on the dual stable isotopes of δ D and δ18O, was employed to estimate groundwater contributions to shallow soil (0–100 cm) water under different groundwater depths. The results revealed that groundwater was the dominant water source (75.7% ± 17.1%) for shallow soil water when the groundwater depth is less than 4 m, indicating that 4 m is a threshold in groundwater depth, separating groundwater‐dependent, and precipitation‐driven vegetation system in the study area. Secondly, a strong nonlinear response was observed between vegetation species, height, coverage, and the decline in groundwater. The vegetation properties were found to be the lowest in the areas where groundwater depth increased from 1.5–4 m to 4–28 m before and after coal mining. Finally, the groundwater level decline in the mining area significantly influenced the groundwater‐dependent vegetation ecosystem, the soil cation exchange capacity and organic matter reduced lead to the degradation of plant communities and the transition of mesophytes to xerophytes. Besides, the soil‐vegetation system in the non‐groundwater‐dependent area has no obvious response to the groundwater decline. These results suggest that caution should be exercised when mining in groundwater‐dependent ecosystem regions.

Environmental DNA, hydrochemistry and stable water isotopes as integrative tracers of urban ecohydrology

Urbanization and the persistent environmental changes present a major challenge for urban freshwaters and availability of water for humans and wildlife. In order to increase understanding of urban ecohydrology, we investigated the variability of planktonic bacteria and benthic diatoms - as two key biological indicators - coupled with insights from hydrochemistry and stable water isotopes across four urban streams characterized by different dominant water sources in Berlin, the German capital, over a period of one year (2021–2022). DNA metabarcoding results show that substantial spatio-temporal variability exists across urban streams in terms of microbial diversity and richness, with clear links to abiotic factors and nutrient concentrations. Bacterial communities showed clear distinction between effluent-impacted and non-effluent impacted streams as well as clear seasonal turnover. In-stream benthic diatom assemblages also showed robust seasonal variation as well as high species diversity. Our multiple-tracer approach is relevant for emerging questions regarding the increased use of treated effluent to supplement declining baseflows, the assessment of stream restoration projects and the impact of storm drainage and surface pollution on aquatic ecosystem health. eDNA analysis allows analysis of spatial and temporal patterns not feasibly studied with traditional analyses of macroinvertebrates. This can ultimately be leveraged for future water resource management and restoration planning and monitoring of urban freshwater systems across metropolitan areas.

Estimasi Angkutan Sedimen Total pada Sungai Indulung Kota Tarakan

As the population increases, the water demand is also increasing. The river flow is the dominant water source to fulfill the needs of human life, so the river should always be kept sustainable, the way to keep is by trying the cross-sectional capacity of the river stable from sediment deposits. Indulung River is one of the rivers in Tarakan City which is experiencing siltation due to sedimentation. Total sediment analysis was conducted to obtain the value of sediment transport and to obtain a method that can be used as a benchmark in determining the total sediment discharge in the Indulung River, using the Yang method and Bagnold method. From the research results, the average sediment discharge using the Yang method is 4.34 tons/year and Bagnold's method is 2.01 tons/year. Based on the recapitulation, which produces the largest value is the Yang method, with a value of 4.34 tons/year, the Yang method is used as a benchmark for other sediment transport methods.

Stable isotopes reveal the surface water-groundwater interaction and variation in young water fraction in an urbanized river zone

Based on 30 sampling campaigns on precipitation, river water and groundwater in Qingbaijiang urban catchment, southwest China, this study reports the spatio-temporal evolution of water isotopes under the impacts of human activities. The seasonal variation of groundwater-surface water interaction is quantitatively evaluated by isotope-aid hydrograph separation, and the young water fraction (Fyw) in river water at different spatial locations is estimated based on the seasonal periodicity of isotopes. The results show that the stable isotopes in river water and groundwater in Qingbaijiang urban catchment grow enriched from upstream to downstream, reflecting the transformation of the dominant water source from plateau river water to local precipitation and the influence of evaporation. The operation of water conservancy projects and construction of impervious surface in urban areas increase the evaporation intensity of river water. The results of the end-member mixing analysis (EMMA) demonstrates that the average annual contributions of river water to near-bank groundwater are 60.17%, 23.55% and 24.90% in the upper, middle and lower parts, respectively. The periodic storage and release of water led by the water conservancy projects enhances the groundwater recharge in the upstream river, while the water exchanges between river water and groundwater in the middle and lower parts of the catchment are reduced. The Fyw at 8 river sections of Qingbaijiang River estimated by the isotopic amplitude ratio method ranges from 0.067 to 0.194, with an overall increasing trend from upstream to downstream. The young water fraction is negatively correlated with mean elevation, mean slope and vegetation coverage, while positively correlated with the proportion of anthropogenic land use and the proportion of low-permeable soil. The construction of impervious surfaces and drainage systems in urban and rural areas is an important driver for the elevated young water fraction.

Water sources, consumption, and water-related sanitation on Pari Island, Indonesia: a mixed-focus group discussion and survey study

Abstract Pari Island has 1,441 inhabitants who are facing major environmental challenges related to water consumption and availability. These challenges may impact water quality and availability in the future. Previous research examining water usage and sanitation behavior on Pari Island remains limited. Since domestic activities dominate in Pari Island, this study evaluated water sources for domestic usage, estimated water consumption, and evaluated sanitation behavior, as well as community behavior and awareness. This study was based on a field survey using a questionnaire involving 317 heads of household, and had focus group discussions. The results revealed that reverse osmosis (RO) water and branded bottled water were the dominant water sources for drinking and food preparation, and RO water had become an important alternative water source for its affordable price. An individual's well water was mostly used for bathing and toilets. Annual water consumption on Pari Island for drinking, food preparation, and water-related sanitation is 24,930.74–29,401.44 m3/year, which still fell within the estimated water capacity of 290,000.48 m3/year, yet problems related to sanitation need special attention with respect to the increasing population. The awareness of the Pari Island community on technological interventions should be an advantage to maintain water sustainability.

Estimasi Angkutan Sedimen Total pada Sungai Indulung Kota Tarakan

As the population increases, the water demand is also increasing. The river flow is the dominant water source to fulfill the needs of human life, so the river should always be kept its sustainability, the way to keep is by trying the cross-sectional capacity of the river stable from sediment deposits. Indulung River is one of the rivers in Tarakan City which is experiencing siltation due to sedimentation. Total sediment analysis was conducted to obtain the value of sediment transport and to obtain a method that can be used as a benchmark in determining the total sediment discharge in the Indulung river, using the Yang method and Bagnold method method. From the research results, the average sediment discharge using the Yang method is 4.34 tons/year and Bagnold's method is 2.01 tons/year. Based on the recapitulation, which produces the largest value is the Yang method, with a value of 4.34 tons/year, so that the Yang method is used as a benchmark for other sediment transport methods.

Assessment of seasonal changes in groundwater quality of waste rock dump in temperate continental climate, northern Japan

Understanding seasonal groundwater quality changes in temperate continental climate waste rock dumps (WRDs) is necessary for sustainable environmental risk prevention and legacy mine contamination management. Therefore, we conducted a field investigation of a WRD to determine the mechanisms controlling its groundwater quality dynamics. The research aimed to understand the impact of seasonal changes on heavy metals released from the WRD. Three monitoring wells were installed in the WRD to investigate the pH, electrical conductivity (EC), and groundwater level (GL). The mineral composition of the waste rock was determined. Groundwater and river water samples from the monitoring wells and rivers surrounding the WRD were collected for chemical analysis. The sphalerite and galena concentrated in the WRD were assumed to be the main sources of Zn, Pb, and Cd contamination. Summer rainfall was the dominant recharge source of river water, which rapidly infiltrated to the WRD, altering the pH, EC, and GL of the groundwater. The pH, EC, and GL were stable in winter because snowpack covering the surface soil prevented groundwater recharge to the WRD. However, snow melting affected the pH, EC, and GL in the WRD. The sources of groundwater recharge (rainfall, river water, and snowmelt) altered the behaviour of the heavy metals in the WRD through two main mechanisms: the dissolution of sulphide minerals and efflorescent salts upon contact with the recharge water, and the dilution effect of the recharge water, which mixes with the groundwater in the WRD, reducing the heavy metal concentration. Sulphide mineral and efflorescent salt dissolution were significant in the deepest monitoring well and rainfall was the dominant recharge source which increased sulphide mineral and efflorescent salt dissolution in the WRD.

Surface‐to‐tile drain connectivity and phosphorus transport: Effect of antecedent soil moisture

AbstractMacropores connecting surface soils to tile drains can alter water and nutrient transport through the subsurface. In this study, laboratory rainfall simulations with artificial macropores combined with edge‐of‐field monitoring were used to evaluate surface‐to‐tile drain connectivity and phosphorus (P) transport as a function of antecedent moisture conditions. Laboratory rainfall simulations using repacked soil boxes with different macropore layouts (i.e., no macropore, surface‐connected macropores, and disconnected macropores) were used to examine changes in water sources and flow pathways to tile drains with varying degrees of connectivity and antecedent wetness. Water, tracer, and P fluxes from a tile‐drained field were also monitored to quantify linkages among water flow pathways, antecedent wetness, and P delivery to tile drains. Both laboratory and field results showed that surface‐to‐tile drain connectivity was important for water transport through the subsurface under both dry and wet antecedent conditions. When soil conditions were dry, discharge was minimal and primarily comprised of event water that bypassed the soil matrix. Increasing wetness resulted in similar event water transport, but greater mobilization of stored pre‐event water and greater discharge; thus, the dominant source of tile water and the magnitude of tile discharge were substantially altered with changing antecedent moisture. Field data revealed that changes in drainage water source and discharge with increasing wetness impacted dissolved P transport. Dissolved P concentration decreased and loading increased with increasing wetness. Findings indicate that greater mobilization of pre‐event water under wet antecedent conditions acted as both a hydrologic and chemical buffer for subsurface dissolved P transport. Comparison of study results to water quality data from a larger edge‐of‐field network suggest that relationships between antecedent moisture conditions, water flow pathways, and P transport from the current study are broadly applicable across tile‐drained fields. Understanding processes controlling P delivery to tile drains has direct applicability for conservation practice implementation and improving process representation in models.

Disentangling runoff generation mechanisms: Combining isotope tracing with integrated surface/subsurface simulation

The majority of runoff studies to date have reported a similar pattern of rapid rain-to-runoff conversion via overland flow and shallow subsurface water flow, as well as the ubiquity of thresholds and hysteresis in rainfall-runoff response. But each of those approaches has limitations in terms of inference and process description. Processes of water transport and mixing and how they influence runoff generation are still not well understood or quantified. In this study, HydroGeoSphere, a fully-integrated surface/subsurface flow model, was used together with stable isotopes for disentangling runoff generation mechanisms in a headwater catchment. The study area (0.21 km2) is the first-level tributary of the Xin’an Jiang River located in a humid climate region of eastern China. Water flow simulation elucidated the spatial water transport process, and isotope tracing quantified the complex water mixing process between the shallow soil and hillslope surface. This study provides insights into the rapid transformation of rainfall infiltration and mixing in soil and exfiltration to a hillslope. Results show that the stream runoff was separated into rainfall-induced overland flow (9 %), exfiltration-induced overland flow (including the 53 % of mixed water from rainfall infiltration and 6 % of the stored soil water), and subsurface flow (32 %). Exfiltration-induced overland flow was the dominant water source in the headwater catchment during a rainfall-runoff event. The mutual influence of rainfall infiltration and soil water exfiltration caused the shallow soil to rapidly become saturated, thus forming saturation excess overland flow. The consistence of estimated soil water velocity based on the integrated isotope and numerical modeling approach, at about 0.4 m/d nearby the stream channel, improved the reliability of model visualizations. Further analysis indicates that water flow paths and velocities responding to the rainfall event were attributed to the soil moisture conditions and topography. This study demonstrates that identifying the rapid mixing processes between the rain and the soil water was crucial for understanding hillslope overland flow and runoff generation in headwater catchments.

Seasonal variations in water uptake and transpiration for plants in a karst critical zone in China

Despite substantial drought conditions in the karst critical zone (KCZ), the KCZ landscapes are often covered with forest woody plants. However, it is not well understood how these plants balance water supply and demand to survive in such a water-limited environment. This study investigated the water uptake and transpiration relationships of four coexisting woody species in a subtropical karst forest ecosystem using measurements of microclimate, soil moisture, stable isotopes (δ18O, δ2H, and δ13C), intrinsic water-use efficiency (WUEi), sap flow, and rooting depth. The focus was on identifying differences within- and between-species across soil- and rock-dominated habitats (SDH and RDH) during the rainy growing season (September 2017) and dry season (February 2018). Species across both habitats tended to have higher transpiration with lower WUEi during the rainy season and lower transpiration with higher WUEi during the dry season. Compared to those in the SDH, species in the RDH showed lower transpiration with higher WUEi in both seasons. The dominant water sources were soil water and rainwater for supporting rainy-season transpiration in the SDH and RDH, respectively, and groundwater was the main water source for supporting dry-season transpiration in both habitats. A clear ecohydrological niche differentiation was also revealed among species. Across both habitats, shallower-rooted species with higher soil-water uptake, compared to deeper-rooted species with higher groundwater uptake, showed higher transpiration and lower WUEi during the rainy season and vice versa during the dry season. This study provides integrated insights into how forest woody plants in the KCZ regulate transpiration and WUEi in response to drought stress through interactions with seasonal water sources in the environment.

Assessment of water quality and challenges for vegetable irrigation in Greater Bandung Area, Indonesia

The high demand of water mainly used for industry and domestic purposes puts pressure on water for agriculture. In addition, the change of massive land use and poor sanitation condition affect the availability of water sources and quality for irrigation. These are very important due to the increase of consumer needs for good, healthy, and safe food, especially for raw vegetables. This study identified water sources and then examined and assessed water quality for raw vegetables irrigation in Greater Bandung Area (GBA) as one of the main vegetable producers in West Java Province. This produced around 2.26-million tons of vegetables in 2019 whose harvest was distributed for local and regional consumption. The research was conducted by field surveys in four vegetable plantations having about 350 farmers, spreading over 3 regencies, Bandung City (city boundary), West Bandung Regency, and Bandung Regency. Water quality was analysed based on National Water Quality Standard Class II and other parameters such as SAR (Sodium Adsorption Ratio), RSC (Residual Sodium Carbonate) and %Na. Field survey showed that farmers used different water sources for agriculture, namely groundwater, springs, lake, and greywater. Assessment of water quality using Pollution Index method showed that the dominant water source was slightly polluted with pollutant parameters of conductivity, BOD, %Na, ammonia, chloride, and sulphate exceeding the standards. It showed possibility of domestic wastewater contamination to irrigation water source. Based on the measured parameters, water used for irrigation, even groundwater, was polluted and might cause potential health risk for consumer.

Coupling water cycle processes with water demand routes of vegetation using a cascade causal modeling approach in arid inland basins

Vegetation degradation is the key cause of land desertification in arid areas. Water stress is one of the most critical factors leading to vegetation degradation. The water needed for vegetation growth is inseparable from the water cycle processes. It is a new scope to reveal the vegetation water demand mechanisms from the water cycle processes. Water cycle processes in arid inland basins can be conceptually separated as RFA (runoff formation area) and RCA (runoff consumption area). In this study, both the water demand mechanisms of natural vegetation and farmland were discovered by creatively constructing the vegetation water demand route model. The TRB (Tarim River Basin), a typical arid inland basin system that RFA is separated from RCA, is considered as the study area. The tendency and relevance of water cycle factors and NDVI were detected. The dominant factors of vegetation growth were identified. According to the interaction causality of water cycle factors and vegetation, the PLS-SEM (partial least squares structural equation models) were constructed in RFA and RCA. Results displayed that SMroot (root-zone soil moisture), groundwater and precipitation were the dominant water sources for natural vegetation in RFA. The water demand for natural vegetation in RCA mainly came from SMroot and that for farmland mainly came from SMsurf (surface soil moisture). New findings showed that blue and green water circulations were more active in RFA than in RCA. Natural vegetation had better adaptability and resilience to water shortages compared with farmland. The higher effect of vegetation on AET (actual evapotranspiration) denoted the better growth status. It is contributed to the rational utilization of water resources in arid basins.

Quantitative Stable Isotope Tracing of Water Uptake in Cynanchum sibiricum during Its Growth Period in Arid Areas of Northwest China

Vegetation root water uptake plays a significant role in water transport processes and has multiple effects along the soil–vegetation–atmosphere interface, particularly in semi-arid and arid ecosystems. The objective of this study was to quantitatively examine the water uptake in Cynanchum sibiricum, a common desert rattan plant in arid regions, during its growth period, as well as to assess the relevance of the contributions of various water sources via a multivariate linear mixed model based on water-stable isotopes and eliminating the significant short-term impact of precipitation pulses on root water uptake. The results indicated that when the influence of a precipitation event was minimized, 0–10 cm soil water was the dominant water source for Cynanchum sibiricum in its growth phase, and that the species’ relative uptake of rainfall was positively proportional to that of 10–70 cm soil water while negatively proportional to that of 0–10 cm soil water. We concluded that Cynanchum sibiricum relies on its active roots extending transversely to extract water from shallow soil to survive under extreme drought conditions and would be inseparable from the symbiosis formed with other deep-rooted vegetation. Additional research into disentangling the water transport processes and studying the ecohydrological feedback along the soil–vegetation interface in arid ecosystems would be beneficial and could contribute to the evidence-based management of water resources for ecological protection.

Middle Pleistocene fluid infiltration with 10–15 ka recurrence within the seismic cycle of the active Monte Morrone Fault System (central Apennines, Italy)

This study integrates field, geochronological and geochemical data to constrain fluid circulation in the damage and core zone of the seismogenic Monte Morrone Fault System (MMFS), central Apennines (Italy). Faulting along the MMFS evolved from a diffuse deformation at the damage zone towards progressive localisation of a narrower fault core and, finally, to (re)activation of discrete slip surfaces at shallower crustal conditions. Multiple generations of carbonate mineralisations, including veins and slickfibers, occur along the main fault surfaces. Carbonate mineralisations are locally fractured and incorporated in the surrounding cataclasites, documenting repetitive structurally-controlled fluid infiltration during transient episodes of permeability creation and destruction. Stable carbon and oxygen isotopes of the carbonate mineralisations document a dominant meteoric water source probably mixed with deeper circulating waters having longer residence time. Clumped-isotope yield formation temperatures of vein and slickenfibers in the range between 23 and 40 °C. U-Th dating of carbonate mineralisations yield Middle Pleistocene ages (from 268 to 189 ka BP), with a 10–15-ka cyclicity that we link to the coseismic rejuvenation of the structural permeability in the fault zone. We propose that fault-related mineralisations recorded the interactions among tectonic deformation and climate during the Quaternary. Our study is the first documentation of fault-controlled recurrence intervals in fluid infiltration in a seismically active fault of central Apennines.

Late Summer Water Sources in Rivers and Lakes of the Upper Yana River Basin, Northern Eurasia, Inferred from Hydrological Tracer Data

Major ions, stable isotopes, and trace elements, including rare earth elements (REEs), are used as natural tracers in the qualitative assessment of potential water sources in lakes and rivers of the upper Yana River basin, between Verkhoyansk and Chersky Ranges, during the late summer period. Three distinct regions were sampled, and a dominant water source in each region was qualitatively inferred from water chemistry data. The REE distribution pattern was found to be highly regional and controlled by pH and carbonate contents. Mountain headwater stream at the Verkhoyansk Range north slope, the Dulgalakh River, shows an input from a mixture of shallow groundwater and icing meltwater, with a depleted isotopic signature (δ18O below –21‰), d-excess (dex = δ2H − 8·δ18O) above 18, enrichment in Mg and Sr, and depletion in heavy REEs. The Derbeke Depression lakes and streams are fed by rainfall having ultra-low total dissolved solids (TDS) content, below 25 mg/L, and a convex-up REE pattern. In a medium mountainous river at the Chersky Range flank, the Dogdo River, leaching through fissured Jurassic carbonates is a dominant runoff pathway. Riverine water is heavily depleted in light REEs, but enriched in Mo, Rb, Sb, W and U. In the Dulgalakh River water, high positive Sm and Gd anomalies were observed, attributed either to local geology (greenshists), historical mining legacy, or contemporary winter road operations.

Co-evolution of the terrestrial and aquatic ecosystem in the Holocene Baltic Sea

Abstract. The Baltic Sea experienced changes in marine input throughout the Holocene as substantial regional ice retreat led to isostatic adjustment, eustatic sea level change, and periodic isolation from the North Sea. Here, we determine the distributions and isotopic signatures of organic compounds preserved in a sediment record spanning the last ∼11 kyr to reconstruct environmental change under these dynamic conditions. Carbon and hydrogen isotope ratios of short-, mid-, and long-chain n-alkanes, along with long-chain diol and glycerol dialkyl glycerol tetraether abundances, were analyzed in sediments sampled from the Arkona Basin in the southwestern Baltic Sea. In the earlier part of the record (specifically 10–8.2 ka), hydrogen isotope values of higher plant-derived n-alkanes revealed a change in dominant water source from an ice-melt-derived to a precipitation-dominated hydrological regime. Following this shift in water source, carbon isotope values of n-alkanes suggest diversification of vegetation. Shifts in hydrology and vegetation did not coincide with established phase boundaries but instead occurred mid-phase or spanned phase transitions. For this reason, we suggest describing the Ancylus Lake in two phases: a meltwater phase (10.6 to 9.2 ka) and a precipitation phase (9.2 to 7.7 ka). Our results highlight the utility of using C and H isotope ratios in conjunction with other compound abundance proxies to better understand the complex environmental change recorded in paleoarchives.

Contribution of winter precipitation to tree growth persists until the late growing season in the Karakoram of northern Pakistan

Identifying the influence of seasonal source water on tree growth is essential to understand the effect of climate change on forest dynamics. However, due to the lack of available long-term monitoring studies, little is known on how long moisture originating from winter precipitation influences tree growth in the following growing season. Herein, we developed a tree-ring latewood oxygen isotope (δ18OLW) chronology from the Karakoram (1955–2013) in northern Pakistan. We investigated whether winter climate signals are incorporated in the δ18OLW and how long winter precipitation through soil moisture contributed to tree growth during the growing season. Significant correlations were found between δ18OLW with both, winter to spring (January–May) temperature (r = 0.43, p < 0.05) and summer (July–August) precipitation (Local: r = −0.38, p < 0.05; Moisture source region: r = −0.44, p < 0.05). As shown by the cross-spectrum and commonality analysis, the climate signals in the δ18OLW are frequency-dependent. Winter temperature signals stored in the δ18OLW variations dominate at low frequencies more than 7 years (59% variance explained), while the summer precipitation signals dominate variations with higher frequencies shorter than 7 years (47% variance explained). Further analysis using reanalysis data shows that the growing season soil moisture at root depth (10–40 cm) is more strongly related to winter precipitation than to summer rainfall. Winter precipitation formed as ground snow provides root-zone soil moisture and tree growth via snowmelt during the growing season. Our study highlights that winter precipitation is the dominant water source contributing to Karakoram tree growth until the late growing season. Given the possibility of a decrease in winter precipitation under climate change in the Karakoram region, local forest is potentially threatened by the declining water supply during the growing season.

Effect of irrigation water withdrawal on the hydrology of the Lake Tana sub-basin

Study regionThe Lake Tana sub-basin, upper Blue Nile, Ethiopia Study focusThe Lake Tana sub-basin is one of the agricultural growth corridors for Ethiopia’s ambitious plan to expand irrigation. Despite the booming irrigation activities in the sub-basin, limited information exists on the rate of irrigation expansion and its impact on the water balance of the sub-basin. This study collected and organized smallholder irrigation data in the sub-basin to identify the actual irrigated area, the abstracted irrigation water, and its implications on seasonal water availability. The area under small-scale irrigation was estimated through data obtained from 'woredas’ (districts) databases. Crop patterns were obtained through field surveys. Irrigation water abstracted at daily timescale was measured. New hydrological insights for the RegionIn the sub-basin, 38,694 ha was under small-scale irrigation in 2020/21. Surface water is the dominant water source, and it supplies about 80% of irrigation withdrawal. Water abstraction for small-scale irrigation is about 430 MCM per dry season (~50% of dry season flow). The eastern side of the sub-basin faces water shortages as the dry season flow is not sufficient for irrigation. With the prospects of more irrigation expansion, small-scale irrigation water withdrawals pose concerns of water scarcity at local level and to the water balance of the sub-basin. Hence, there is urgent need for adaptive management of the small-scale irrigation effect on the sub-basin’s hydrology.