A National Scale Assessment of Temporal Variations in Groundwater Discharge to Rivers: Malawi

This study investigates groundwater discharge to rivers in the Shire River Basin, Malawi, using the base flow index (BFI) approach. The BFI represents the baseflow component of a river and is often used as a proxy indicator of groundwater discharge to a river. The smoothed minima method was applied to river flow data from 15 gauges in the Basin (ranging from 1948 to 2012) and the Mann-Kendall (MK) statistical test was used to identify trends in the BFI. The BFI results indicate that groundwater plays an important role in contributing to river flows in the SRB, especially in the dry season. Expressing the BFI as a percentage, these values indicate that annual groundwater discharge to the river's ranges from 19% in the Rivirivi River to 97% in the Shire River. Seasonally, minimal difference was found between the annual and the wet season BFI. Generally, the dry season BFI was higher than those of the wet season with most rivers increasing to >75%. Groundwater data supported the seasonal fluctuations identified in the BFI data, however, there were no groundwater monitoring boreholes in close proximity to any of the river gauges for in-depth analysis. The results also showed long term trends in the BFI data indicating behavioural changes in the river baseflow and groundwater discharge. In some areas, the declines in BFI indicate that groundwater discharge has been reducing over time due to declines in groundwater levels. This is a concern for the sustainable management of water resources in the Basin. The findings of this study provide important new knowledge on the seasonal and long-term behaviour of groundwater discharge to rivers in the Basin which will be crucial for supporting sustainable water resources management practices. The results will be particularly useful to the new National Water Resources Authority within the Malawian Government, who will oversee catchment management plans.

This study investigated how sporadic river datasets could be used to quantify temporal variations in the base flow index (BFI). The BFI represents the baseflow component of river flow which is often used as a proxy indicator for groundwater discharge to a river. The Bua catchment in Malawi was used as a case study, whereby the smoothed minima method was applied to river flow data from six gauges (ranging from 1953 to 2009) and the Mann-Kendall (MK) statistical test was used to identify trends in BFI. The results showed that baseflow plays an important role within the catchment. Average annual BFIs > 0.74 were found for gauges in the lower reaches of the catchment, in contrast to lower BFIs < 0.54 which were found for gauges in the higher reaches. Minimal difference between annual and wet season BFI was observed, however dry season BFI was >0.94 across all gauges indicating the importance of baseflow in maintaining any dry season flows. Long term trends were identified in the annual and wet season BFI, but no evidence of a trend was found in the dry season BFI. Sustainable management of the investigated catchment should, therefore, account for the temporal variations in baseflow, with special regard to water resources allocation within the region and consideration in future scheme appraisals aimed at developing water resources. Further, this demonstration of how to work with sporadic river data to investigate baseflow serves as an important example for other catchments faced with similar challenges.

The U.S. Geological Survey, in cooperation with the Oklahoma Water Resources Board, investigated trends in base flow, total flow, and base-flow index of selected streams in Oklahoma and evaluated possible causes for trends. Thirty-seven streamflow-gaging stations that had unregulated or moderately regulated streamflow were selected for trend analysis. Statistical evaluation of trends in annual and seasonal (winter-spring and summer-autumn) base flow, total flow, and base-flow index at 37 selected streamflow-gaging stations in Oklahoma was performed by using a Kendall's tau trend test. This trend analysis also was performed for annual and seasonal precipitation for nine climate divisions in the study area, annual peak flows, the number of days where flow was zero or less than 1 cubic foot per second (both annually and seasonally), and annual winter groundwater levels for 35 shallow wells near the analyzed stations. Precipitation-adjusted trends using LOESS regressions and Kendall's tau were computed for annual and seasonal base-flow and total-flow volumes in order to identify the presence of underlying trends in streamflow that are not associated with annual or seasonal variations in precipitation. In general, upward trends in precipitation were detected for climate divisions in north-central Oklahoma and south-central and southeastern Kansas. More climate divisions had statistically significant upward trends in total precipitation for annual water years than in winter-spring or summer-autumn water years. Significant trends in annual or seasonal base-flow volume were detected for 22 stations, 19 of which had trends that were upward in direction. Significant trends in annual or seasonal total-flow volume were detected for 14 stations, 9 of which had trends that were upward in direction. Most stations that had significant upward trends in annual or seasonal total-flow volume also had significant upward trends in base-flow volume for the same period. Precipitation adjustment changed the results (significant only or significance and direction) of significant annual or seasonal trends in unadjusted base-flow volume for 12 stations and in unadjusted total-flow volume for 13 stations. Significant trends in annual or seasonal base-flow index were detected for 25 stations, 23 of which had trends that were upward in direction. Eighteen stations that had significant upward trends in annual or seasonal base-flow index also had significant upward trends in base-flow volume and no significant downward trends in total-flow volume during the same period, which indicated that upward trends in base-flow index were likely driven by increases in base flow at these stations. Trend results were highly variable throughout the State. However, some recurring patterns in locations of stations with similar trend results were detected. In general, significant downward trends in base-flow and total-flow volumes were detected for the three stations in the Oklahoma Panhandle. Significant upward trends in annual or seasonal base-flow volume before and after precipitation adjustment were detected for 12 stations in southwestern and central Oklahoma. In eastern Oklahoma, significant upward trends in annual or seasonal base-flow volume were only detected for 4 stations, and significant upward trends in annual or seasonal total-flow volume were only detected for 1 station. After precipitation adjustment no stations in this region had significant upward trends in either parameter, one station had significant downward trends in annual base-flow volume, and one station had significant downward trends in winter-spring total-flow volume. Increases in annual and seasonal precipitation, especially during a substantial wet period (1980-2000), may be one of the factors resulting in upward trends in base-flow volume and total-flow volume at many of the stations analyzed in this report. Eleven stations with significant upward trends in precipitation-adjust

چکیده سابقه و هدف : شناخت و درک رابطه بین مولفه‌های مختلف حوضه می‌تواند به بهبود و توسعه پیش‌بینی‌ها‌ در حوضه‌های فاقد آمار کمک کند. مقدار واقعی جریان پایه نامشخص است و نظر به اینکه منحنی تداوم جریان با استفاده از داده‌های مشاهداتی تهیه می‌شود، لذا شناخت و تحلیل روابط بین شاخص‌های منحنی تداوم جریان با شاخص جریان پایه منجر به دست‌یابی به اطلاعاتی برای استفاده بهینه از شاخص‌های منحنی تداوم جریان به‌عنوان پارامتر برآورد کننده شاخص جریان پایه، خواهد شد. هدف از این پژوهش، بررسی و شناخت رابطه شاخص جریان پایه با شاخص‌های منحنی تداوم جریان در اقالیم مختلف کشور ایران می‌باشد. مواد و روش‌ها: ابتدا با تهیه نقشه اقلیم کشور و تقاطع آن با مرز حوزه‌های آبخیز رتبه چهار، حوضه‌های واقع در هر منطقه اقلیمی تفکیک شد. سپس تعداد حداقل سی ایستگاه با آمار مناسب و دوره مشترک آماری سال‌های1355-1390در هر منطقه اقلیمی انتخاب شد. منحنی تداوم جریان با استفاده از داده‌های دبی روزانه بلند‌مدت، ترسیم و شاخص‌های,Q2, Q5,Q10, Q15,Q20,Q50,Q75,Q90‌ استخراج شد. شاخص آخرین نقطه عطف منحنی تداوم جریان(QFinal) در محل شیب صفر منحنی با استفاده از کد‌نویسی در محیط متلب، استخراج شد. سپس شاخص جریان پایه با استفاده از الگوریتم فیلتر رقومی برگشتی تک پارامتره با استفاده از داده‌های دبی روزانه بلند مدت محاسبه شد. سرانجام روابط رگرسیونی بین شاخص‌های منحنی و میانگین سالانه شاخص جریان پایه در مناطق مختلف اقلیمی استخراج و تحلیل شد. یافته‌ها: نتایج نشان داد که بیشترین همبستگی بین شاخص‌های منحنی تداوم جریان با شاخص جریان پایه در حوضه‌های منطقه بسیار‌مرطوب با ضریب تبیین 84/0 مربوط به شاخص‌های دوره پرآبی منحنی است ولی در دو منطقه مرطوب و نیمه‌مرطوب، بیشترین همبستگی مربوط به شاخص دوره کم‌آبی با ضریب تبیین 63/0 و 69/0 است. بیشترین ضریب تبیین بین شاخص منحنی در نقطه شیب صفر با شاخص جریان پایه، مربوط به منطقه بسیار‌مرطوب به میزان 85/0 است. در جمع‌بندی کلی نتایج قابل ذکر است که روابط همبستگی بین شاخص-های بخش انتهایی منحنی تداوم جریان با میانگین سالانه شاخص جریان پایه، در حوضه‌های اقالیم مرطوب، نیمه‌مرطوب، مدیترانه‌ای و نیمه‌خشک، یک رابطه قوی و قابل توصیه برای مقاصد تحلیل منطقه‌ای و پیش‌بینی و برآورد می‌باشد. ولی در حوضه‌های منطقه خشک این رابطه دارای استثناء است و شاخص‌های بخش پرآبی منحنی این نقش را به عهده دارند. در حوضه‌های منطقه بسیار‌مرطوب، ضریب تبیین کلیه شاخص‌های منحنی تداوم جریان با شاخص جریان پایه، قابل اعتماد و استفاده است. نتیجه‌‌گیری: در جمع‌بندی کلی نتایج، قابل ذکر است که روابط همبستگی بین شاخص‌های بخش انتهایی و موسوم به کم آبی منحنی تداوم جریان با میانگین سالانه شاخص جریان پایه، در حوضه‌های اقالیم مرطوب، نیمه‌مرطوب، مدیترانه‌ای و نیمه‌خشک، یک رابطه قوی و قابل اعتماد و توصیه برای تحلیل منطقه‌ای و پیش‌بینی و برآورد می‌باشد. ولی در حوضه‌های منطقه خشک این رابطه دارای استثناء است و شاخص‌های بخش پرآبی منحنی، این نقش را به عهده دارند، و بیشترین همبستگی را به خود اختصاص داده‌اند. در حوضه‌های واقع در منطقه بسیار‌مرطوب نیز ضریب تبیین کلیه شاخص‌ها با شاخص جریان پایه دارای قابلیت اعتماد و استفاده است. نتایج کلی در حوضه‌های تمامی مناطق اقلیمی، پارامتر شاخص‌های منحنی تداوم جریان را به‌عنوان پارامتر قابل اعتماد و پیش‌بینی کننده شاخص جریان پایه، نشان می‌دهد. واژه‌های کلیدی: برآورد، تفکیک هیدروگراف جریان، شاخص جریان پایه، شاخص منحنی تداوم جریان، همبستگی

The groundwater and surface water interface has been proved evident by the existence of effluent and influent streams. Still, the irrigation sector in sub-Saharan Africa, Tanzania included, is predominantly using surface water and groundwater conjunctively without a clear understanding of the contribution of each of the two water sources. This study was conducted to analyze the water exchange processes between groundwater and surface water in the Usangu Plains. Constrained by data scarcity in the study area, only three hydrograph separation techniques (Sliding interval, Fixed interval, and Local minimum) of the Baseflow Index model third version (BFI+ 3.0) were used. These techniques were applied to estimate baseflow, surface runoff and baseflow indices using river discharge data from six gauging stations across six different rivers. Further, the Mann-Kendall (MK) test was used for trend analysis of the long-term time series baseflow index. Results indicate that the groundwater-surface water interaction exists and the baseflow contributes substantially to the sustainable river flows in the Usangu Plains during both dry and wet seasons. Except for the Great Ruaha River at Msembe, the other five rivers manifested a great reliance on the baseflow with more than 90% of it in the river flows. The MK test revealed that at annual, wet, and dry season scale there are statistically non-significant increasing and decreasing trends in the baseflows. Land and water management strategies such as water allocation measures, sound water usage practices and afforestation may be better approaches to counteract the declines of water flows in rivers of the Usangu Plains, especially in the dry season.

The study aimed to determine pathological conditions across two seasons, leading to condemnations of beef edible red offals in Kgatleng District, Botswana. Offals are valued in communities of Botswana. Data from slaughter facilities was evaluated for dry/winter and wet/summer seasons. Financial losses were also determined. 7405 cattle were processed in the two seasons, with 4005 cattle slaughtered in the dry season and 3400 in the wet season. Of the slaughtered cattle, 55.2% (2209) of the dry season and 45% (1531) of the wet seasonhad some forms of pathological conditions that led to condemnations of the offals. Lungs were highly condemned at 26.2% in the wet season and 32.7% during the dry season, followed by livers at 16.2 and 18.4% in the wet and dry seasons, respectively. Emphysema led to a condemnation rate of lungs at 20% and 17% for the dry and wet seasons, respectively. The least condemned offals were the spleen at 2.3% (wet season) and 2.1% (dry season), followed by the kidneys at 0.3% (wet season) and 2% (dry season). Financially, the dry season losses were relatively higher at BWP62 950.55 compared to the wet season at BWP43 863.95. Management strategies should be put in place to avail offals to consumers. Key words: Beef, edible red offals, pathological conditions, wet and dry seasons.

Enhanced low flow prediction for water and environmental management

Aims: This study investigates the microorganisms associated with hospital wastewaters collected from the Offa Local Government Area of Kwara State, Nigeria, during the wet and dry seasons.
 Study Design: This project was a cross sectional descriptive study in which subjects were hospital wastewater samples collected from the study site.
 Place and Duration of Study: the samples were analyzed in the department of microbiology, Federal University of Technology, Akure, Ondo State, Nigeria.
 Methodology: Microbiological study of one hundred and twenty-six samples of hospital wastewater collected both during wet season and dry season periods in the years 2018 – 2019 from Offa Local Government Area of Kwara State, Nigeria, was carried out using conventional and molecular techniques respectively and the Global Positioning System (GPS) of each collection site was accurately recorded.
 Results: The microbial load of wet season samples collected from Offa Local Government Area ranged between 7±4,00 and 150±43.59 while that of dry season samples ranged between 10±2.00 x 105 and 225±67.27 (x 105cfu/ml). The bacteria isolated from wet season samples included; Alcaligenes faecalis, A. aquatilis and Staphylococcus saprophyticus with percentage occurrences of 65.4, 19.2 and 15.4 respectively, while bacteria isolated from dry season sample were A. faecalis and S. saprophyticus with percentages occurrence of 79.17 and 20.89, respectively.
 Conclusion: The findings from this study showed that hospital wastewater collected during dry season period had more bacterial load than that of wet season period. The findings also confirmed A. faecalis as the most predominant and prevailing bacteria inhabiting hospital wastewater. Thus, care must be taken by avoiding hospital wastewater from getting into the municipal water supply to prevent infections associated with A. faecalis, A. aquatilis and S. saprophyticus.

Biotic and abiotic properties most closely associated with subtropical forest soil respiration differ in wet and dry seasons: A 10-year in situ study

Background and Objectives: Water and soil are fundamental components of ecosystems, crucial for maintaining agricultural productivity, biodiversity, and human livelihoods. This study aims to observe the seasonal dynamics of water quality and embankment soil along the Gorai River, Kushtia, Bangladesh. Methods: A total of 15 water samples and 15 embankment soil samples were collected along the river for both dry (January- February 2024) and wet (July- August 2023) seasons following random sampling techniques. The water and soil samples were analyzed at the Environmental Analysis Laboratory of Islamic University, Kushtia, and the regional laboratory of SRDI, Kushtia, Bangladesh respectively. To identify the relationship among variables, one-way ANOVA, Pearson correlation, and principal component analysis (PCA) were computed for this study. Results: The results show that some parameters of water samples such as turbidity, total suspended solids (TSS), total dissolved solids (TDS), chemical oxygen demand (COD), and electrical conductivity (EC) exhibit significant differences for both dry and wet seasons except dissolved oxygen (DO) and hardness; whereas, pH, EC, calcium (Ca), copper (Cu), iron (Fe), and manganese (Mn) of soil samples show differences for both seasons. The correlation analysis reveals a robust correlation between EC and TDS and turbidity and TSS in water samples from both the dry and wet seasons. Furthermore, a strong positive correlation exists between organic matter (OM) and total nitrogen (N2), and both seasons show a positive correlation between Cu and Fe. The PCA analysis indicates that salinity-related factors such as EC and TDS greatly influence water quality during the dry season. In contrast, there is greater variability during the wet season, with N2, phosphorus (P), and OM playing significant roles due to increased moisture and nutrient dynamics of soil samples. Conclusion: This study’s outcomes revealed that electrical conductivity (EC) showed significant differences for both soil and water samples in dry and wet seasons. This study will contribute to sustainable water and soil resource management by identifying the key seasonal elements affecting water quality and soil fertility in the Gorai River region.

Nitrate is a limiting nutrient for plant growth and vital for crop production to increase agricultural productivity. However, its excessive presence in aquatic environment poses risk turning in to major aquatic ecosystem perturbation. Dissolved nitrate from lands to waterways is mainly exported via runoff and leaching. The transport of nitrate in a river is a function of the streamflow rate and its concentration, which render to the seasonal variation. Therefore, the aim of this study was to assess the seasonal variation of flow and nitrate flux. Streamflow data of the Gilgel Gibe River for the period of two years (2013-2014) were used. The baseflow is separated using Web-based Hydrograph Analysis Tool (WHAT). Dissolved nitrate concentrations measured on daily basis were also used. The effects of storm events on flow and nitrate transport were examined during dry and wet seasons. The river had shown high discharge rate from the mid June to late October. The baseflow index (BFI) was found 0.76 indicating that the streamflow is mainly controlled by groundwater discharge. Similarly, during the dry seasons, total nitrate input was considerably less than in wetter seasons. Nitrate concentrations, however, were unusually high in the first summer storm runoff after the dry season. The average annual nitrate loads varied from 13761.2 ton to 156.45 ton during the wet and dry seasons respectively. The regression curve for the nitrate load against streamflow (r2=0.88) has shown significant relationship (p-value=0.000). In the time interval studied, over 95% of the nitrate was transported from the watershed during the wet seasons of greater rainfall, which disclosed that seasonality and river flow are primary forcing functions when considering nitrate loadings in this watershed

River ecological flow early warning forecasting using baseflow separation and machine learning in the Jiaojiang River Basin, Southeast China

The southwestern mountains of Hainan Island are the southernmost region with tropical karst landform in China. The frequent alternation of dry and wet seasons leads to the loss of the mineral nutrients of limestone, creating karst fissure habitats. Plants living in karst fissure habitats for long periods of time have developed local adaptation mechanisms correspondingly. In the paper, hydrogen–oxygen stable isotope technology was applied to determine the water-use sources of Impatiens hainanensis in the dry and wet seasons, hoping to expound the adaptation mechanism of I. hainanensis in karst fissure habitats to the moisture dynamics in the wet and dry seasons. In the wet season (May to October, 2018), the air humidity is relatively high in the I. hainanensis habitat; in the dry season (November 2018 to April 2019), there is a degree of evaporation. In the wet season, fine-root biomass increases with soil depths, while coarse-root biomass decreases with soil depths; in the dry season, fine-root biomass is lower and coarse-root biomass is higher compared with the wet season. It was found that the average rainfall reached 1523 mm and the main water-use sources were shallow (0–5 cm) and middle (5–10 cm) soil water, epikarst water, and shallow karst fissure water during the wet season; the average rainfall reached 528 mm, and the deep (10–15 cm) soil water and shallow karst fissure water were the main water-use sources during the dry season. Fog water has a partial complementary effect in the dry season. The differences in the distribution of root biomass and each source of water in the wet and dry seasons of I. hainanensis also reflect the different water-use strategies of I. hainanensis in the wet and dry seasons. In both dry and wet seasons, I. hainanensis formed a water-use pattern dominated by soil water and shallow fissure water (0–15 cm) under the influence of the “fissure-soil-plant” system in the karst region.

First posted August 13, 2015 Revised October 26, 2015 For additional information, contact: Director, Virginia Water Science Center U.S. Geological Survey 1730 East Parham Road Richmond, VA 23228 http://va.water.usgs.gov In response to challenges to groundwater availability posed by historic land-use practices, expanding development of hydrocarbon resources, and drought, the U.S. Geological Survey Groundwater Resources Program began a regional assessment of the Appalachian Plateaus aquifers in 2013 that incorporated a hydrologic landscape approach to estimate all components of the hydrologic system: surface runoff, base flow from groundwater, and interaction with atmospheric water (precipitation and evapotranspiration). This assessment was intended to complement other Federal and State investigations and provide foundational groundwater-related datasets in the Appalachian Plateaus. A regional Soil-Water-Balance model was constructed for a 160,000-square-mile study area that extended to the topographic divide of all streams originating outside but flowing into areas underlain by Appalachian Plateaus aquifers. The model incorporated soil, landscape, and climate variables to estimate an annual water budget for the 32-year period from 1980 to 2011 and was calibrated using base-flow data estimated by hydrograph separation techniques from 20 streamflow gaging stations across the study area. Over this period, an average of 47 inches per year (in/yr) of precipitation fell on Appalachian Plateaus aquifers. Simulations from the regional Soil-Water-Balance model indicate that only 19 percent of the precipitation or an average 9 in/yr recharged aquifers, and 19 percent resulted in surface runoff to streams. The remaining 62 percent, an average of 27 in/yr of water, was returned to the atmosphere via evapotranspiration. Because withdrawals from aquifers due to pumping equated to less than 1 percent of the water budget, differences in predevelopment and postdevelopment regional water budgets of the Appalachian Plateaus were minimal. Storage changes caused by filling of abandoned coal-mine aquifers and long-term differences in aquifer storage resulting from climate fluctuations constitute a small portion of the overall water budget. The percentage of precipitation that results in recharge, runoff, or evapotranspiration from the landscape varies annually by up to a factor of two depending on temporal changes in prevailing climate conditions and spatial changes in basin characteristics, precipitation patterns, and sources of atmospheric moisture over a large study area. A comparison of water-budget estimates from the regional Soil-Water-Balance model for a dry year (1988) and wet year (2004) showed that evapotranspiration accounts for most of the annual differences in precipitation. As a portion of annual precipitation, evapotranspiration ranged from 69 percent (dry year) to 52 percent (wet year), a range four times greater than the 15 percent (dry year) to 18 percent (wet year) range estimated for recharge. Evapotranspiration as a percentage of precipitation peaks during dry periods, whereas base flow and runoff tend to reach minimum values. During wet periods, this relationship is reversed and base flow and runoff as a percentage of precipitation generally peak while evapotranspiration percentages reach minimum values. Annual recharge in the Appalachian Plateaus reaches a maximum at near 20 percent of annual precipitation, regardless of the severity of wet conditions. Hydrograph separation data from 849 streamflow gaging stations in the study area were used to assess trends in streamflow, base flow, surface runoff, and base-flow index, or ratio of base flow to streamflow, in the Appalachian Plateaus for the period from 1930 to 2011. Annual data anomalies for each of the four variables were individually defined as the annual standard deviation from the mean at all 849 streamflow gaging stations. Annual data anomalies confirm the close relation of annual precipitation to both base flow and runoff components of streamflow, and both components increased during the period of analysis. Around 1970, conditions shifted streamflow from values generally below to above long-term means. At a regional scale, increases in base flow account for most of these observed increases in mean annual streamflow. The independence of the base-flow index to annual climate trends indicate that changes in the components of streamflow of the Appalachian Plateaus are probably in response to shifts in seasonal precipitation or widespread land-use practices. A subset of 77 index streamgages, defined as having 60 or more years of complete record between the years 1930 and 2011 with no more than 20 percent missing data, was selected to show spatial patterns of change in the water budget. Data from the index streamgages showed that the overall trends in base flow are dependent upon the period of evaluation. Long-term (1930–2011) increases in base flow were observed throughout the study area. For two shorter periods (1930–1969 and 1970–2011) trends in base flow were largely negative. In general, spatial patterns of change in streamflow, base flow, and runoff were mixed but generally consistent with prevailing climate patterns and land-use changes.

The Base-Flow Indices (BFI), indicating surface and groundwater interaction, play a significant role in the hydrological cycle. The values vary widely across the globe, and are expected to change in the context of a changing climate. Predicting global “natural” BFI is challenging due to limited observations reflecting natural impacts. This study aims to predict annual BFI and their trends for a compiled dataset of annual streamflow and meteorological data covering the period 1982-2020 for more than 2250 small unregulated catchments worldwide. BFI were derived using three digital filtering methods, resulting in a trend of -0.0009 ± 0.01 per decade over the last four decades. To predict annual BFI and their trends in ungauged catchments, a Random Forest Regression approach was employed, incorporating static attributes and meteorological time series data as model inputs. Five-fold cross-validation demonstrated the effectiveness of the Random Forest Regression in predicting both BFI and their trends. The Quantile Regression Forest method was utilized to quantify the uncertainty, achieving a relatively low range for both BFI and their trends. Soil conditions and maximum temperature emerged as the most crucial variables for predicting BFI, while temperature-related variables also proved essential for predicting the BFI trends. The goal is to extend the understanding of "natural" BFI and their trends in ungauged catchments, as the Random Forest Regression model was trained under unregulated conditions. This study offers the possibility to predict "natural" BFI and their trendsacross the globe. This could support water authorities in managing water resources, particularly concerning base flow.