Wet Months Research Articles

The impact of climate change and potential distribution of the endangered white winged wood duck (Asarcornis scutulata, 1882) in Indian eastern Himalaya

The White-Winged Wood duck (Asarcornis scutulata) is an endangered forest wetland bird currently on the verge of extinction due to an array of anthropogenic pressures. It has been reported that global climate change could affect the distribution of many bird species globally. Therefore, an understanding the potential distribution of the White-Winged Wood duck in future climate scenarios could facilitate the creation of immediate conservation plans and the mitigation of subsequent threats. This is the first ever study on the distribution of White-Winged Wood Duck (WWWD) where Representative Concentration Pathway (RCP) 8.5 scenario was used to forecast the distribution of the WWWD in the Indian Eastern Himalayan region in the 2050s and 2070s. The study revealed that 1.87 % of the total area of IEH has the high potential distribution of WWWD. The state of Assam alone includes 1.68 % of the highly potential habitat in the region. It was predicted that 436.61 km2 of highly potential habitat would be lost by 2070. Changes in the annual temperature range, precipitation in the wettest months (June to September), and precipitation decrease in the warmest quarter (October to December) would result in the loss of highly potential habitats. Under the influence of climate change, the habitat of WWWD in the eastern part of the region is likely to shift towards the western part. It was found that there will be a decline in potential habitat in the Indian states of Arunachal Pradesh, Assam, Nagaland, and Tripura located in the IEH under future climate scenarios. The potential of areas located at the Bhutan and Assam border would increase for supporting WWWD as this species' requires the average annual precipitation about 1000–1200 mm. However, the simultaneous anthropogenic activity would further destroy potential habitats in the future. The current study has provided baseline data on the potential distribution of WWWD in the IEH region for immediate conservation management plans.

Microscopic analysis of Trichosanthes dioica

One of the most nutrient-dense cucurbit vegetables is the pointed gourd (Trichosanthes dioica Roxb.), which enjoys a prized spot in the Indian market during the warm and wet months. It is a perennial crop that is quite popular because it is available for eight months out of the year (February–September). It has certain medical effects due to its high protein and vitamin A content, and there are numerous studies about its involvement in decreasing blood sugar levels. In this paper, an effort was made to examine the microscopic characteristics of Trichosanthes dioica. Leaf exhibited uniceriate glandular epidermis with a single cellular head. Spongy parenchymatous cells, collenchymatous cells, pericycle, phloem, and xylem were all present after the epidermis. The Xylem vessels were spiral and reticulate. The collenchymatous cells' inside. The existence of uniseriate multicellular trichomes was shown by powder microscopy. crystal sheath oil globules, anomocytic stomata, liginified spiral arteries, and epidermis cells. The powders were subjected to various reagent treatments during the powder analysis, and various colours were visible to the naked eye and under UV light. There was quantitative microscopy. Vein termination and vein islet averages were 13.6 and 12, respectively. The upper and lower epidermis of the leaf had average stomatal counts of 12.5 and 16.33, respectively. The upper and lower epidermis of the leaf had average stomatal indices of 22.87 and 24.62, respectively. Data from these studies were helpful for evaluating the raw materials used in the manufacturing of herbal medicines and for anatomical research.

Global potential distribution of Oryctes rhinoceros, as predicted by Boosted Regression Tree model

Climate change is expected to have a significant influence on species range expansion, habitat shifts, and risk of biological invasion due to changes in survival rates, and rapid reproduction. This will tend to affect their geographical distribution and dispersal patterns, thereby threatening agriculture production and food security. Therefore, it is essential to understand the impact of climate change on the range shifts of an invasive species like the Asiatic rhinoceros beetle, Oryctes rhinoceros Linnaeus (Coleoptera: Dynastinae: Scarabaeidae), to inform policy formulation and preventive measures. To achieve this, we used environmental variables and occurrence records of O. rhinoceros to predict the current and future potential distribution of the pest under two representative concentration pathways (RCPs 4.5 and 8.5) for three time periods (2030, 2050, and 2080). We employed Boosted Regression Tree (BRT) and ArcGIS to create risk maps for the pest. The BRT model predicts an expansion of O. rhinoceros outside the current known distribution. The environmental variables which contributed the most to the geographical distribution of the pest were minimum temperature of coldest month (26.81 %), followed by precipitation of wettest month (20.61 %), temperature annual range (11.34 %), mean diurnal range (11.33 %), and elevation (4.49 %). Under the different climate change scenarios, O. rhinoceros will continue to threaten the economically important host plants until 2080. As a result, there will be a need for effective strategies to prevent its spread. Our predictions are reliable and have the potential to estimate the global distribution of the pest, as well as provide suggestions for prompt of O. rhinoceros prevention and management.

Intra-seasonal rainfall and piped water revenue variability in rural Africa

Rainfall patterns influence water usage and revenue from user payments in rural Africa. We explore these dynamics by examining monthly rainfall against 4,888 records of rural piped water revenue in Ghana, Rwanda, and Uganda and quantifying revenue changes over 635 transitions between dry and wet seasons.Results show operators experience revenue variability at regional and intra-seasonal scales. Revenues fall by an average of 30 percent during the wettest months of the year in climate regimes with consistent wet season rainfall. However, seasonally stable revenues are observed in areas where consecutive dry days are common during the wet season, potentially reflecting a dependency on reliable services. We also find changes in tariff level, waterpoint connection type, and payment approach do not consistently prevent or increase seasonal revenue variability.Local revenue generation underpins delivery of drinking water services. Where rainfall patterns remain consistent, piped water operators can expect to encounter seasonal revenue reductions regardless of whether services are provided on or off premises and of how services are paid for. Revenue projections that assume consistent volumetric demand year-round may lead to shortfalls that threaten sustainability and undermine the case for future investment. Intra-seasonal rainfall analysis can enhance rural piped water revenue planning by offering localised insight into demand dynamics and revealing where climate variability may increase dependency on reliable services.

Niche and range dynamics of Tasmanian blue gum (Eucalyptus globulus Labill.), a globally cultivated invasive tree.

The ecological niche concept has provided insights into various areas in ecology and biogeography. Although there remains much controversy regarding whether species niches are conserved across space and time, many recent studies have suggested that invasive species conserve their climatic niche between native and introduced ranges; however, whether the climatic niche of cultivated invasive species, whose niches are strongly affected by human activities, are conserved between native and introduced ranges remains unclear. Additionally, the range dynamics of invasive species in their native and introduced regions have not been extensively studied. Here, we investigated the niche and range dynamics of Tasmanian blue gum (Eucalyptus globulus Labill.), a globally cultivated invasive tree, using ecological niche models and niche dynamic analyses. The most important factors affecting the niche changes between native and introduced Tasmanian blue gum were max temperature of the warmest month and precipitation of the wettest month. The climate niche was not conserved between introduced and native range Tasmanian blue gum; moreover, the niche area of the former was ca. 7.4 times larger than that of the latter, as introduced Tasmanian blue gum could survive in hotter, colder, wetter, and drier climates. In addition, the potential range of introduced Tasmanian blue gum was ca. 32 times larger than that of its native counterpart. Human introduction and cultivation may play a key role in the niche and range expansion of introduced Tasmanian blue gum. Given that small increases in niche area can result in large range expansions, the niche expansion of an invasive species could be used to evaluate invasion risk, which might even be more sensitive than range expansions.

Seasonal changes in semen characteristics of pure and crossbred rabbit bucks fed graded levels of vitamin C under heat stress conditions

The experiment was carried out to investigate the effect of season and graded vitamin C levels on semen quality of rabbit bucks in the Northern Guinea Savanna of Nigeria. A total of 55 rabbit bucks consisting of 40 pure New Zealand White (NZW) and 15 New Zealand x California (NZW×CAL) crossbreds were used for the study. The duration of the study spanned the hot dry (March-May) and cool wet (June-August) seasons. The traits investigated were semen motility, concentration, volume, pH, colour, live and dead sperm. Results obtained showed that vitamin C had significant (p<0.01) effect on semen characteristics. There was a progressive increase in semen motility, concentration and live sperm and decrease in dead sperm as vitamin C level increased. Semen volume deviated from this pattern while colour was consistent all through. The result on monthly variation indicated that volume increased during the months of March to May ranging between 1.32-1.43 ml while during the months of June to August, it oscillated between 0.41 - 0.95 ml. Sperm concentration significantly (p<0.05) increased from the hot dry months (75.72-129.48x106) to the cool wet months (98.17-102.78x106) while colour remained consistent with an increase in live sperm cells. There was significant (p<0.001) interaction between vitamin C level and season on sperm motility, concentration and live sperm being better in the hot dry (70.9%, 114.5x106, 85.31%) and cool wet (76.3%, 121.6x106, 90.14%) seasons on 400 mg/kg feed vitamin C. Sperm volume was higher on 100 mg/kg feed vitamin C in the hot dry (1.60 ml) and cool wet (0.98 ml) seasons and 400 mg/kg feed in the hot dry (1.57 ml) and cool wet (0.77 ml) than other levels. Based on the results, it is concluded that vitamin C improved the semen characteristics of rabbit bucks at 400 mg/kg feed during the hot dry season which translates to improved semen quality.

Habitat suitability mapping of the Indian giant flying squirrel (Petaurista philippensis Elliot, 1839) in India with ensemble modeling

Flying squirrels are one of the least studied mammalian taxa in South Asia as well as in India owing to their nocturnal, arboreal and cryptic nature. We applied ensemble species distribution modeling using BIOMOD2 (ver 1.0) R-package to predict the suitable habitat of the Indian giant flying squirrel (Petaurista philippensis, Elliot 1839) in Indian biogeographic regions and states, and to identify the physical variables that define its fundamental niche. A subset of least correlated variables from bioclimatic (mean diurnal temperature range, temperature isothermality, precipitation of wettest month, precipitation of driest month and precipitation of warmest quarter, and precipitation of coldest quarter), topographic (elevation), water-related (distance to major water streams), and vegetation-related (NDVI, and vegetation height) data sets were used in the modeling. The accuracy of the final ensemble habitat suitability model was characterized by the receiver operating characteristic curve (ROC) and true skill statistic (TSS). In India, a total of highly suitable habitat for the species was estimated to be 66,743 sq. km, varying between states and biogeographic regions. Final model revealed that predictive suitable habitat of the species was limited primarily to the southern peninsula, including the Western Ghats, the Deccan peninsula, and the semi-arid region, and to a lesser extent, the coastal areas of the Kerala state. At the state level, majority of suitable habitat for the species estimated in Kerala followed by Karnataka, Tamil Nadu, Gujarat, Maharashtra, Rajasthan, and Madhya Pradesh. Climatic factors, particularly temperature and precipitation, have been identified as major determinants of Indian giant flying squirrel's potential habitat. We suggest that several new areas in the modeling that showed suitable habitat for the species necessitate immediate attention to validate species occurrence through field work. Extensive further studies on the species could also provide a detailed insight into the species' dispersion, colonization and the effect of future climate change in the Indian subcontinent.

Seasonal Ecosystem Productivity in a Seasonally Dry Tropical Forest (Caatinga) Using Flux Tower Measurements and Remote Sensing Data

The Caatinga dry forest encompasses 11% of the total continental territory of Brazil. Nevertheless, most research on the relationship between phenology and ecosystem productivity of Brazilian tropical forests is aimed at the Amazon basin. Thus, in this study we evaluated the seasonality of ecosystem productivity (gross primary production—GPP) in a preserved Caatinga environment in northeast Brazil. Analyses were carried out using eddy covariance measurements and satellite-derived data from sensor MODIS (MODerate Resolution Imaging Spectroradiometer, MOD17 and MOD13 products). In addition to GPP, we investigated water use efficiency (WUE) and meteorological and phenological aspects through remotely sensed vegetation indices (NDVI and EVI). We verified that ecosystem productivity is limited mainly by evapotranspiration, with maximum GPP values registered in the wetter months, indicating a strong dependency on water availability. NDVI and EVI were positively associated with GPP (r = 0.69 and 0.81, respectively), suggesting a coupling between the emergence of new leaves and the phenology of local photosynthetic capacity. WUE, on the other hand, was strongly controlled by consecutive dry days and not necessarily by total precipitation amount. The vegetation indices adequately described interannual variations of the forest response to environmental factors, and GPP MODIS presented a good relationship with tower-measured GPP in dry (R2 = 0.76) and wet (R2 = 0.62) periods.

Seroprevalence and Risk Factors for Toxoplasma gondii and Neospora caninum in Cattle in Portugal

Simple SummaryNeospora caninum and Toxoplasma gondii are apicomplexan parasites with a worldwide distribution and both infect cattle. While the importance of N. caninum is mainly linked to reproductive losses, concern has been raised about the role of beef as a source of food-borne toxoplasmosis in humans. Little is known about the prevalence of these parasites in cattle in Portugal. This study aimed to evaluate the seroprevalence and risk factors for N. caninum and T. gondii in naturally exposed cattle from different geographical areas in the country. Results point to a low but widespread seroprevalence of T. gondii, while that of N. caninum was found to be in the same range as reported in other Mediterranean countries. Distribution of both parasites may be explained by common climate factors and management practices identified as significant predictors of infection in the study.Neospora caninum has a worldwide economic impact as an important cause of abortion in cattle, while Toxoplasma gondii, another abortifacient pathogen, is globally a major foodborne zoonotic threat. The study aimed to evaluate the seroprevalence and risk factors for the two parasites in cattle in Portugal. A total of 612 sera from 35 farms were tested by an in-house p30 ELISA for T. gondii and p38 ELISA for N. caninum. T. gondii positive and suspicious sera were confirmed by p30 Western blot or IFAT. T. gondii and N. caninum animal seroprevalence was 9.2% (95%CI 7.1–11.7) and 17.2% (95% CI 14.4–20.4) and herd seroprevalence was 51.4% (95% CI 35.6–67.0) and 68.6% (95% CI 52.0–81.5), respectively. At the univariable level, climate area and precipitation of wettest month, driest month, driest quarter, and warmest quarter were significant predictors of seropositivity for both. N. caninum seropositivity was more likely in the region Norte, densely populated areas, and intensive production, and the probability of T. gondii seropositivity decreased with herd size. Results confirm the need to consider neosporosis in the differential diagnosis of cattle reproductive disorders in Portugal and may be valuable to inform source attribution models for human toxoplasmosis.

Effect of Near-Earth Surface Temperature on Soil Temperature at 5 cm Depth

The research investigates the effects of ground surface temperature (air temperature) on soil temperature at a depth of 5 cm. The study covers a period of fourteen (14) months from May 2010 to June 2011 in Akure, Southwestern Nigeria. With the aid of an automatic weather station, temperature readings were taken at a depth of 5 cm below the soil surface at five (5) minute intervals daily. It was also observed that many analyses of soil temperature are based on the theories of heat flow and energy balance. The study reveals that surface temperature has a weak effect on soil temperature. The best correlation coefficient obtained for the study period is about 0.56 with a quadratic equation of order 2 at 5% significance level. This implies that air temperature cannot be solely used to predict soil temperature at a depth of 5 cm. A study of diurnal variation reveals that air temperature is usually higher than soil temperature during the day, and vice versa. The study also revealed that surface and soil temperatures are generally lower during the wet months when compared with the dry months. The wet season average daily temperatures are 23.42oC and 27.69oC for air and soil while the corresponding dry season values are 33.92oC and 30.91oC respectively. The results are recommended for agricultural purposes such as determination of soil and environmental conditions for crop production.

Incorporating interspecific relationships into species distribution models can better assess the response of species to climate change, a case study of two Chinese primates

Whether the distribution of species can track future changes in climate will ultimately determine their survival. However, traditional predictions of species distributions in response to climate change often ignore the effects of biotic interactions. Here, we incorporated interspecific competition into SDMs (Species distribution models) to assess the distribution of two species endemic to China, namely the Sichuan snub-nosed monkey (Rhinopithecus roxellanae) and Tibetan macaque (Macaca thibetana), in response to climate change. Due to overlap areas in the distributions of both species, niche competition between the Sichuan snub-nosed monkey and Tibetan macaque was observed, and the former was less competitive in terms of theirability to source food and their reproductive capacity. The area where niche overlap between the Sichuan snub-nosed monkey and Tibetan macaque occurs accounts for half of the suitable habitat for the former, suggesting that the Sichuan snub-nosed monkey cannot use this habitat effectively. Both species are predicted to lose more than 70 % of their suitable habitat by the 2050s, and the altitude of suitable habitat will likely decrease. Bio3 (Isothermality) and Bio13 (Precipitation of Wettest Month) were the most important climatic variables affecting the distribution of the Sichuan snub-nosed monkey and Tibetan macaque, respectively. The suitable habitat of the Sichuan snub-nosed monkey and Tibetan macaque was fragmented into several isolated pieces, which requires that ecological restoration should be carried out in advance. We demonstrated that the incorporation of interspecific competition into SDMs can accurately assess the response of species to future climate change, as less competitive species cannot effectively use their suitable habitat.

Rainfall variability and trends in the Borana zone of southern Ethiopia

Abstract This paper has examined the variability and trends of rainfall in the Borana zone, southern Ethiopia. Monthly rainfall data from 1981 to 2018 were obtained from the National Meteorological Agency (NMA) of Ethiopia. Mean, standard deviation and coefficient of variation were employed to analyze temporal variability. Mann–Kendall (MK) test and Sen's slope estimator (SEE) were used to determine trend and its magnitude, respectively. The inverse weighting distance (IDW) interpolation technique was employed to generate surface data and produce spatial rainfall maps. April and Belg were the wettest month and season, respectively. On an annual basis, Arero (741 mm) followed by Teltele (629 mm) were the wettest stations, whereas the Dillo station (285 mm) was the driest. Rainfall is highly variable on a monthly and seasonal basis than annual timescale. Meher rainfall has shown a significant rainfall increase (P-value <0.05) at most stations. A significant increase in annual rainfall was observed at Arero, Dehas, Dillo and Miyo. Spatially, rainfall decreases from the northeast and northwest parts of the Borana towards the southwest. The findings of this study can serve as a reference basis and provides useful information for policymakers to devise and implement better water management strategies in this water-scarce region.

Integrated SWAT-MODFLOW model to study saltwater intrusion in Da Nang coastal city

This study applied an integrated surface water-groundwater (SW-GW) model, SWAT-MODFLOW to study interaction of surface and groundwater than simulate saltwater intrusion at a regional scale in Da Nang coastal city, center of Vietnam. Model components were calibrated and validated using monthly river flow data and hydraulic head data for the 2005-2020 period and showed good agreement with observed data. The results demonstrated that GW-SW exchange in the upstream areas had the most pronounced fluctuation between the wet and dry months under historical conditions. The combined potential impact is that intensive groundwater use may have more immediate effects on river flow than those of climate change, which has important implications for water resources management and supply in the future. The results showed that the total average recharge to groundwater from the rivers was varied from 12046 to 23147 m3/d relative to 50 – 74% of water resources in rain and dry season. Saltwater intrusion intrusion in 2020 is about 100 km2. In the area of Son Tra and Ngu Hanh Son districts, groundwater pumping must be reduced to zero, in some other areas, pumping rate do not exceed 250 to 1000 m3/day with distance to coastline at least 500 to 1400m depends on each area.

Thermal bioclimatic indicators over Southeast Asia: present status and future projection using CMIP6.

Mapping potential changes in bioclimatic characteristics are critical for planning mitigation goals and climate change adaptation. Assessment of such changes is particularly important for Southeast Asia (SEA) - home to global largest ecological diversity. Twenty-three global climate models (GCMs) of Coupled Model Intercomparison Project Phase 6 (CMIP6) were used in this study to evaluate changes in 11 thermal bioclimatic indicators over SEA for two shared socioeconomic pathways (SSPs), 2-4.5 and 5-8.5. Spatial changes in the ensemble mean, 5th, and 95th percentile of each indicator for near (2020-2059) and far (2060-2099) periods were examined in order to understand temporal changes and associated uncertainty. The results indicated large spatial heterogeneity and temporal variability in projected changes of bioclimatic indicators. A higher change was projected for mainland SEA in the far future and less in maritime region during the near future. At the same time, uncertainty in the projected bioclimatic indices was higher for mainland than maritime SEA. Analysis of mean multi-model ensemble revealed a change in mean temperature ranged from - 0.71 to 3.23°C in near and from 0.00 to 4.07°C in far futures. The diurnal temperature range was projected to reduce over most of SEA (ranging from - 1.1 to - 2.0°C), while isothermality is likely to decrease from - 1.1 to - 4.6%. A decrease in isothermality along with narrowing of seasonality indicated a possible shift in climate, particularly in the north of mainland SEA. Maximum temperature in the warmest month/quarter was projected to increase a little more than the coldest month/quarter and the mean temperature in the driest month to increase more than the wettest month. This would cause an increase in the annual temperature range in the future.

Patterns and Driving Factors of Diversity in the Shrub Community in Central and Southern China

Climate, topography, and human activities are known to influence plant diversity. In the present study, species-abundance distribution (SAD) patterns of the shrub community were fitted, and the mechanism of contribution of 22 driving factors was assessed. The results showed that the α-diversity index exhibited no significant differences between artificial disturbance and the natural community. The Zipf and Zipf–Mandelbrot models were found to exhibit a good SAD fitting of the communities, thereby exhibiting a different diversity structure. It was observed that the SAD followed more than one rule, and the Zipf–Mandelbrot model was better than other models. The gradient boosting model indicated that precipitation in the wettest month, annual precipitation, and slope direction showed the strongest impact on plant richness. The indicator species of the artificial disturbance and natural community were identified from a multiple regression tree. Furthermore, an increase in species diversity was observed with a rise in latitude, exhibiting a single-peaked curve with increased altitude. β-diversity analysis indicated that both habitat filtering and the neutral effect influenced the establishment of the natural community, while the establishment of the artificial disturbance community was only affected by habitat filtering. Our study provides a better understanding of the ecological process of the maintenance of shrub-community diversity.

Hydrological Retrospective and Historical Drought Analysis in a Brazilian Savanna Basin

Analyzing historical droughts is essential to improve the assessment of future hydrological risks and to understand the effects of climate variability on streamflow. However, prolonged and consistent hydrological time series are scarce in the Brazilian savanna region. This study aimed to analyze the performance of climate reanalysis products in precipitation estimation, hydrological modeling, and historical drought analysis in a Brazilian savanna basin. For this purpose, precipitation data from the twentieth-century atmospheric model ensemble (ERA-20CM) and the land component of the fifth generation of European ReAnalysis (ERA5-Land) with bias correction were used. The weather variables were obtained from the Climatic Research Unit (CRU) and the hydrological modeling was performed using the Soil and Water Assessment Tool (SWAT). The Standardized Streamflow Index (SSI) was used to calculate hydrological drought in the basin. Overall, ERA5-Land performed satisfactorily in precipitation estimation, mainly on the monthly time scale, hydrological modeling, and drought prediction. Since ERA-20CM showed unsatisfactory values for the performance statistics in all analyses, the hydrologic drought (1950 to 2018) was performed with ERA5-Land. The results showed both an increase in the number of dry months and a decrease in wet months in recent decades.

Diversity and seasonality of adult caddisflies (Trichoptera) captured by light-trapping beside streams in the Darwin region of northern Australia

Caddisflies comprise a major component of the macroinvertebrate diversity of streams throughout the world. We studied temporal variation in the abundance and diversity of caddisflies of six streams in the monsoonal wet-dry tropics of northern Australia. Abundance and diversity of adult caddisflies were highly seasonal with most activity within wet season months from January to April, with a synchronous pulse of activity in the mid-dry season in two of the three years of study at some sites. Modelling of species richness showed variability among sites in the seasonal patterns of species richness. Multivariate analysis identified seasonal change in assemblage composition. These results are relevant to the design of biodiversity studies on seasonally flowing streams. Surveys of caddisfly diversity are most effectively undertaken during and after the wet season: repeated surveys are required to maximise the detection of the full suite of species occurring at a site.

Water quality index assessment methods for surface water: A case study of the Citarum River in Indonesia

Water quality index (WQI) can express overall water quality status in a single term. As such, the application of daily WQI assessment should help the general public be more aware of the condition of the surface water around them. As the longest and biggest river in the West Java Province, the Citarum River plays an important role in the life of the community and ecosystem around it. Therefore, this research evaluated which WQI assessment method was best suited for determining the Citarum River's water quality. We utilized West Java Province monitoring data collected from four monitoring stations along the Upstream Citarum. The WQI was calculated using the National Sanitation Foundation WQI (NSF WQI), Canadian Council of Ministers of the Environment WQI (CCME WQI), and Oregon Water Quality Index (OWQI) assessment methods. Nine years of monitoring data were grouped and analyzed according to wet vs. dry months, wet vs. dry years, monitoring station, and year. Using the NSF WQI assessment method, the Citarum River obtained a ‘Fair’ and ‘Bad’ water quality grade with WQI ranging between 38.212 and 60.903 during dry months, 49.089 and 62.348 during wet months, 42.935 and 65.696 during dry years, and 39.002 and 58.898 during wet years. The data ranged from 41.458 and 61.206 from each monitoring station, and between 35.920 and 58.713 for the data from each monitoring year. The CCME WQI assessment method showed that the Citarum River had ‘Fair’, ‘Marginal’, and ‘Bad’ water quality with WQI ranging between 12.683 and 31.503 during dry months, 21.231 and 33.127 during wet months, 12.683 and 31.503 during dry years, 12.134 and 28.748 during wet years, 13.621 and 30.569 for the data from each monitoring station, and 13.219 and 68.808 for the data from each monitoring year. The OWQI assessment method gave the Citarum River a ‘Very Bad’ water quality rating with WQI ranging between 11.528 and 18.827 during dry months, 13.898 and 24.563 during wet months, 11.528 and 25.782 during dry years, 11.528 and 15.997 during wet years, 11.528 and 18.842 for each monitoring station, and 11.523 and 16.528 for the data from each monitoring year. Based on these results and the collated advantages and disadvantages of each method, the NSF WQI assessment method was deemed to be the best for determining the Citarum River's water quality.

Effect of soil thickness on rainfall infiltration and runoff generation from karst hillslopes during rainstorms

AbstractKnowledge of water movement from the hillslope critical zone is important for water management. However, the runoff process resulting from extreme rainfall events remains unclear due to rare field‐based natural monitoring data. We investigated rainwater infiltration and runoff generation processes in two plots with deep and relatively shallow soil thicknesses (66 vs. 35 cm depth on average, respectively) on karst hillslopes. Rainwater, soil water and lateral discharge runoff in the soil‐epikarst system were monitored using hydrometric and 18O isotope methods in September 2020, which was the wettest month on record at the study s, including three normal rainfalls (29.6 mm in 8.5 h, 25 mm in 8.5 h, and 27.4 in 3.5 h) and three extreme rainstorms (335 mm in 11.5 h, 77.8 mm in 9 h, and 129.2 mm in 5 h). Soil moisture and water table responded rapidly (<30 min) during the extreme rainfall. However, the soil‐epikarst interface exhibited the strongest stability (coefficient variation [CV] < 8.18%) and collected more pre‐event water, reflected by the isotopic signature of the soil water. Accordingly, low permeability at the soil‐epikarst interface played an important role in buffering rainwater infiltration. Controlled by infiltration‐excess and saturation‐excess runoff mechanisms, the contribution of surface runoff to total discharge was less than 3% during normal rainfall events, which was significantly less than that during extreme rainfall events (13%–60%). This was supported by the evolution of δ18O values of surface runoff that were similar to rainwater and more 18O‐depleted than that of subsurface runoff. Higher rainfall intensity which exceeded soil permeability during extreme rainstorms further increased the possibility of exceeding infiltration‐saturation processes. For the deep soil plot (DSP), surface runoff (>44%) dominated the extreme rainfall process; while for the shallow‐soil plot (SSP), surface runoff (60%) dominated only during the maximum rainfall events. Moreover, the surface runoff contribution to total runoff in DSP was greater than that in SSP. Surface runoff from slopes with thicker soil layers is an important part of karst watershed flood processes in extreme rainfall events, which should be considered carefully for water resource management.Highlights Hydrometric and isotope methods are used to assess extreme hydrological processes. The surface runoff of extreme rainfalls is much higher than that of normal rainfall. The infiltration‐excess mechanism dominates the surface runoff of extreme rainfall. Slopes with thicker soil layers are more vulnerable to flooding in the karst region.

Influence of Rainfall and Spatial Temporal Distribution Analysis of Total Suspended Solid in Laut Tawar Lake

Total Suspended Solid (TSS) is a solid particle suspended in the water column of organic and inorganic materials, sized more than two micrometers. The high concentration of TSS in the waters causes a decrease in water clarity and potentially reduces dissolved oxygen that can threaten the life of aquatic biota. This study aims to analyze the spatial and temporal distribution of TSS and analyze the influence of rainfall on TSS in Laut Tawar Lake waters. The lake TSS ranged from 44 – 91 mg/L with an average of 68.67 ± 11.23 mg/L. Spatially TSS ranged from 63.17 - 73.67 mg/L and temporally ranged from 51.14 - 81.43 mg/L. The distribution of TSS was not spatially different because the lake waters are perfectly agitated. The difference in TSS was obtained temporally due to the influence of rainfall. The catchment area can be eroded by only 100 mm of rain/month. It leads to high production of TSS loading into the lake waters. It was indicated by the difference in TSS of Dry Months with TSS of Wet and Moist Months. The determinant coefficient of influence of rainfall on the TSS concentration of the lake waters is 0.62.