Central Valley Research Articles

Modeling Groundwater Levels in California's Central Valley by Hierarchical Gaussian Process and Neural Network Regression

AbstractModeling groundwater levels continuously across California's Central Valley (CV) hydrological system is challenging due to low‐quality well data which is sparsely and noisily sampled across time and space. The lack of consistent well data makes it difficult to evaluate the impact of 2017 and 2019 wet years on CV groundwater following a severe drought during 2012–2015. A novel machine learning method is formulated for modeling groundwater levels by learning from a 3D lithological texture model of the CV aquifer. The proposed formulation performs multivariate regression by combining Gaussian processes (GP) and deep neural networks (DNN). The hierarchical modeling approach constitutes training the DNN to learn a lithologically informed latent space where non‐parametric regression with GP is performed. We demonstrate the efficacy of GP‐DNN regression for modeling non‐stationary features in the well data with fast and reliable uncertainty quantification, as validated to be statistically consistent with the empirical data distribution from 90 blind wells across CV. We show how the model predictions may be used to supplement hydrological understanding of aquifer responses in basins with irregular well data. Our results indicate that on average the 2017 and 2019 wet years in California were largely ineffective in replenishing the groundwater loss caused during previous drought years.

Overview of the Current Challenges in Pulmonary Coccidioidomycosis.

Coccidioidomycosis is a disease caused by soil fungi of the genus Coccidioides, divided genetically into Coccidioides immitis (California isolates) and Coccidioides posadasii (isolates outside California). Coccidioidomycosis is transmitted through the inhalation of fungal spores, arthroconidia, which can cause disease in susceptible mammalian hosts, including humans. Coccidioidomycosis is endemic to the western part of the United States of America, including the central valley of California, Arizona, New Mexico, and parts of western Texas. Cases have been reported in other regions in different states, and endemic pockets are present in these states. The incidence of reported cases of coccidioidomycosis has notably increased since it became reportable in 1995. Clinically, the infection ranges from asymptomatic to fatal disease due to pneumonia or disseminated states. The recognition of coccidioidomycosis can be challenging, as it frequently mimics bacterial community-acquired pneumonia. The diagnosis of coccidioidomycosis is frequently dependent on serologic testing, the results of which can take several days or longer to obtain. Coccidioidomycosis continues to present challenges for clinicians, and suspected cases can be easily missed. The challenges of coccidioidomycosis disease, from presentation to diagnosis to treatment, remain a hurdle for clinicians, and further research is needed to address these challenges.

Outbreak of Chikungunya Fever in the Central Valley of Chiapas, Mexico.

The first ever recorded outbreak of Chikungunya virus (CHIKV) in the highlands (central valley of Chiapas) Mexico took place in 2015. Clinical data from 80 infected patients together with information provided from virus isolates offered a vision of the diseased and their response linked to different variables such as age, gender, association with pre-existing diseases of some patients, including CHIKF-DENF co-infection. The origins of the Tuxtla Gutierrez CHIKV viruses isolated in the study, including other Mexican isolates, were traced to viruses circulating in regions of Asia in Micronesia and Philippines. Also, we call the attention of the influx of migrants coming from countries having current explosive outbreaks of CHIKV and DENV in the Americas and into southern Mexico. Further we discuss vulnerabilities and point out specially to the geographic location of Chiapas State and its strategic position for attracting the human migrant population.

Neogene surface uplift of the Lunpola Basin in Central Tibet: Implications for uplifting and flattening of orogenic plateaus

Orogenic plateaus are known for their high and flat interiors, but the mechanism by which the high-elevation, low-relief topography is formed remains controversial. The Tibetan Plateau, which may have had a broad central valley along the Bangong suture zone during the Eocene, is a valuable research target to test potential driving mechanisms. In this study, we report both stable and clumped isotopes of lacustrine carbonates of the Lunpola Basin to better constrain the paleoelevation history of the Bangong suture zone in Central Tibet. Covariations of the stable oxygen and carbon isotopes indicate increasing evaporative enrichment of lake water reflecting enhanced aridity from the middle Eocene to early Miocene. After removing altered samples using multiple diagenesis screening methods and the potential influence of global cooling, our clumped isotope temperatures indicate consistent paleoelevations of 2.2 ± 1.1 km at 40–20 Ma, followed by an abrupt 1.4 ± 0.8 km surface uplift at 20–19 Ma and an additional 1.0 ± 0.7 km surface uplift between 16 Ma and the present to achieve the current high elevation of ∼4.6 km. These new paleoelevation results suggest that the Neogene was the primary period of topographic growth for the Lunpola Basin, which contradicts previous inferences emphasizing Paleogene growth. We argue that the Bangong suture zone in Central Tibet was probably a broad low-elevation valley throughout the Paleogene and uplifted mainly during the Neogene by multiple subsurface geodynamic processes, including convective removal of the lower lithosphere and middle–lower crustal flow. A comparison with the north-central Tibet Hoh Xil Basin and South American Altiplano indicates that these subsurface geodynamic processes may be common for uplifting and flattening orogenic plateaus.

Precipitation in Kathmandu Valley: A Spatial-temporal Study

Over the past decade, advancements in atmospheric research have significantly improved the analysis of precipitation monitoring, understanding climate trends and variability, and identifying climatic anomalies associated with dry and wet periods. A key objective of this research is to enhance the understanding of precipitation patterns in the Kathmandu Valley, particularly in relation to the placement of gauges for long-range predictions and subsequent forecasting challenges. This study focuses on the evolving patterns of precipitation across the three districts within the Kathmandu Valley, the most developed and densely populated area in Nepal, encircled by four mountain ranges. We employ interpolation methods in ArcGIS Pro to identify, estimate, and forecast precipitation trends, and use the Mann-Kendall test to reveal statistically significant trends and provide insights into broader climatic processes. The research analyzes trends in both seasonal and annual precipitation and temperature across four time periods—pre-monsoon, monsoon, post-monsoon, and winter—using the Mann-Kendall test. The analysis reveals a decreasing trend in monthly rainfall from 2003 to 2017 at the majority of stations (14 stations out of 19), with areas along the valley slopes receiving significantly more precipitation compared to the central valley. The results of this study contribute to a deeper understanding of climate change in the Kathmandu Valley.

Redesigning and validation of fertilizer use in maize for variable plant densities in central rift valley and Jimma in Ethiopia.

Due to low adoption and sub-optimal fertilizer use and planting density recommendation in maize, redesigning and testing these technologies are required. The study was conducted to evaluate redesigned fertilizer use of maize in two pant densities (32,443 and 53,333 plants ha-1 in Central Rift Valley (CRV); 27724 and 62,000 plants ha-1 in Jimma) on farmers' fields in contrasting agro-ecologies of Ethiopia. The on-farm study was conducted in the 2017 and 2018 cropping seasons with 3 × 2 fertilizer and plant density, factors in both regions of Ethiopia. In redesigned fertilizer use, nutrients were estimated based on the target yield. In this study, 40.8, 0.0, and 12.2 kg ha-1 N, P, and K were estimated for the redesigned fertilizer use in CRV (50% of water-limited potential yield (Yw) = 3.1 t ha-1) whereas in Jimma (50% of Yw = 7.5 t ha-1) 149.8, 9, 130.6 kg ha-1 N, P and K were estimated to produce the 50% of Yw. Linear mixed modeling was used to assess the effect of fertilizer-plant density treatments on maize yield and nutrient use efficiency. The result revealed that the average estimated maize yield for WOF, FFU, and RDFU fertilizer treatments were 2.6, 3.6, and 4.5 t ha-1 under current plant density (32,443 plants ha-1) in CRV whereas the average yields of these treatments were 3.2, 4.5 and 4.5 t ha-1 respectively when maize was grown with redesigned plant density (53,333 plants ha-1) in the same location. The average maize yield with WOF, FFU, and RDFU were 3.0, 4.6, and 4.6 t ha-1 with 27,774 plants ha-1 plant density in Jimma whereas the average maize yields over the two seasons with the same treatments were 4.3, 6.0 and 8.0 t ha-1 respectively when the crop is planted with 62,000 plants ha-1 plant density. The RDFU and redesigned plant density resulted in significantly higher yield compared to their respective control CRV but RDFU significantly increased maize yield when it was planted at redesigned (62,000 plant ha-1) in Jimma. FFU and RDFU were economically viable and redesigned plant density was also a cheaper means of improving maize productivity, especially in the Jimma region. Soil organic carbon and N were closely related to the grain yield response of maize compared to other soil factors. In conclusion, this investigation gives an insight into the importance of redesigned fertilizer use and redesigned plant density for improving maize productivity and thereby narrowing the yield gaps of the crop in high maize potential regions in Ethiopia like Jimma.

Isogeochemical Characterization of Mountain System Recharge Processes in the Sierra Nevada, California

AbstractMountain System Recharge processes are significant natural recharge pathways in many arid and semi‐arid mountainous regions. However, Mountain System Recharge processes are often poorly understood and characterized in hydrologic models. Mountains are the primary water supply source to valley aquifers via lateral groundwater flow from the mountain block (Mountain Block Recharge) and focused recharge from mountain streams contributing to focused Mountain Front Recharge at the piedmont zone. Here, we present a multi‐tool isogeochemical approach to characterize mountain flow paths and Mountain System Recharge in the northern Tulare Basin, California. We used groundwater chemistry data to delineate hydrochemical facies and explain the chemical evolution of groundwater from the Sierra Nevada to the Central Valley aquifer. Stable isotopes and radiogenic groundwater tracers validated Mountain System Recharge processes by differentiating focused from diffuse recharge, and estimating apparent groundwater age, respectively. Novel application of End‐Member Mixing Analysis using conservative chemical components revealed three Mountain System Recharge end‐members: (a) evaporated Ca‐HCO3 water type associated with focused Mountain Front Recharge, (b) non‐evaporated Ca‐HCO3 and Na‐HCO3 water types with short residence times associated with shallow Mountain Block Recharge, and (c) Na‐HCO3 groundwater type with long residence time associated with deep Mountain Block Recharge. We quantified the contribution of each Mountain System Recharge process to the valley aquifer by calculating mixing ratios. Our results show that deep Mountain Block Recharge is a significant recharge component, representing 31%–53% of the valley groundwater. Greater hydraulic connectivity between the Sierra Nevada and Central Valley has significant implications for parameterizing groundwater flow models. Our framework is useful for understanding Mountain System Recharge processes in other snow‐dominated mountain watersheds.

Regional Comparisons of Sensitivities of Phytophthora citrophthora and P. syringae Causing Citrus Brown Rot in California to Four New and Two Older Fungicides.

Isolates of the citrus brown rot pathogens Phytophthora citrophthora and P. syringae from the Inland Empire (IE) and Ventura Co. (VE) regions of southern California were evaluated for their sensitivity to ethaboxam, fluopicolide, mandipropamid, and oxathiapiprolin, and the previously published baselines that were generated for Central Valley (CV) isolates of California were expanded. Fungicides were generally more toxic to CV isolates of both species for all four fungicides. Specific differences were found in the toxicity of ethaboxam to P. syringae where CV isolates on average were 6.8 or 8.2 times more sensitive than those from the VE or IE regions, respectively. Based on the grouping of isolates in an unweighted pair-group method with arithmetic mean (UPGMA) dendrogram, as well as fastStructure analyses and plotting of principal component analyses (PCAs), differences in ethaboxam sensitivity could be related to differences in genetic background of the isolates. Isolates of P. citrophthora from the IE and VE had slightly reduced (i.e., 1.5×) sensitivity to mandipropamid as compared with isolates from the CV and were found on distinct branches in the UPGMA dendrogram. Differences in genetic background of less sensitive isolates within each species indicate that these two phenotypes emerged multiple times independently. IE and VE isolates of both species were sensitive to mefenoxam. Moderate resistance to potassium phosphite (EC50 values of 25 to 75 μg/ml) was present in IE and VE isolates of P. syringae, whereas some IE isolates of P. citrophthora were considered resistant with EC50 values of up to 113.69 μg/ml. Resistance to potassium phosphite did not relate to distinct genotypes.

Electric field dependence of the electron drift velocity in n-type InxGa1-xAs1-yBiy epilayer

The effect of Bi incorporation into InxGa1-xAs lattice on the nanosecond pulsed electric field dependence of the drift velocity of electrons in n-type InxGa1-xAs1-yBiy alloys with various doping densities is investigated at room temperature. The electronic band structure of the alloys is calculated by Finite Element Methods (FEM). The electron temperature is determined from analytical modeling of the power dissipation mechanism. The drift velocity of the electrons (vdrift) does not saturate up to 5.4 kV/cm electric field for the lowest doping density sample. The sample is burned out at a higher electric field due to the impact ionization mechanism. However, the vdrift saturates at a high electric field region in the samples with higher doping densities, and the saturation of electric field values of vdrift depends on the doping density for these samples. The highest electron drift mobility (μdrift) is obtained as 6236 cm2/Vs for the sample with the lowest electron density. The heating of the only electrons through the applied electric field is not enough to initiate inter-valley transfer because of scatterings during transport. Hence, the electric field dependence on electron transport occurs only in the central valley. The effect of the scatterings on the electron transport is identified by considering ionized impurity and phonon scatterings.

Landscape structure of the Middle Lena valley

In this article we present the results of landscape structure study in the Middle Lena valley (Erkeni, Ensieli and Tuimaada), made using GIS mapping based on Sentinel 2 satellite images and ASTER GDEM datasets. Alas complexes and croplands were identified using K-means image segmentation with different initial numbers. Three machine learning algorithms were tested for pixel-based land cover classification. The best result was achieved with the Support Vector Machine classifier. The mapping revealed the landscape structure of 20 spatial units, which were organized into groups of upland, alas, slope, valley and floodplain landscapes. The contrasting landscape structure of the Middle Lena valley was revealed. The northern Ensieli valley is characterized by the predominance of forest larch-pine landscapes, alas complexes mostly dry with steppe meadows are widespread in the watershed. The slopes are dominated by larch forests with patches of birch. The central Tuimaada valley is the most anthropogenically transformed, here steppe meadows and anthropogenic steppes dominate. The plateau part is mainly forested with croplands. The southern valley of the Erkeni is characterized by the smallest area of the valley part dominated by steppe meadows, the slopes of the main bank of the southern and south-eastern exposition are covered with xerophytic meadows. The landscape structure of valleys, floodplain and plakor parts largely determines the specifics of agricultural land use of the local population. The results obtained can be used for further research into the response of permafrost landscapes of the Middle Lena valleys to increased anthropogenic pressure in the context of climate change.

Modeling performances of maize cultivars under current and future climate scenarios in southern central Ethiopian rift valley

BackgroundIn southern central rift valley of Ethiopia, maize is an important crop because of its adaptation to wider agro-ecologies and higher yield potential. However, most cultivars were not parameterized to include in the database of Decision Support System for Agro-technology Transfer (DSSAT). As a result simulation of growth and yield of those cultivars was not possible under changing climate.MethodsTwo set of independent crop, management and soil data were used for calibration and validation of genetic coefficients of maize cultivars (BH-540, BH-546, BH-547, Shala and Shone) under condition of historic weather (1990–2020). Later, we simulated the growth and yield of maize using twenty multimodel climate ensembles across RCP 4.5 and 8.5 during early, medium and late century across Shamana, Bilate, Hawassa and Dilla clusters using DSSATv4.8 model.ResultsCultivars BH-540, BH-546, BH-547, Shala and Shone produced yields of 5.7, 5.4, 5.2, 6.9 and 7.4 t ha−1 with the corresponding error percentage of − 0.1, − 0.8, − 1.0, − 6.1 and 2.6%. The results of normalized root mean square were 1.14–4.2 and 3.0–3.9%, for grain yield during calibration and validation, respectively showing an excellent rating. The simulation experiment produced 5.4–9.2 t ha−1 for grain yield of maize cultivars across the study areas, which is likely to fall close to 63.3% by 2070 if right adaptation options are not introduced necessitating switch in cultivars and production areas.ConclusionsThere is critical need for reduction of GHGs emissions, generation of innovative adaptation strategies, and development of drought and heat stress tolerant maize cultivars. Hence, researchers and policy makers shall act with utmost urgency to embark with breeding programs that target climate change adaptation traits in maize crop.

Provenance Analysis in the Nima Basin during Paleogene and Its Implications for the Decline of the Tibetan Central Valley.

It is unclear what caused the Bangong Nujiang suture zone in the central Tibetan plateau to rise from less than 2 km in early Cenozoic to more than 4 km at present. The zircon U-Pb ages and trace elements of samples from the Niubao Formation in the Paleogene of the Nima basin were analyzed and tested. Combined with the isostasy theory, the surface uplift height of the Nima Basin during the Cenozoic period was calculated. The zircon U-Pb age results of the Niubao formation are consistent with the ages of the Lhasa terrane on the south side of the basin, the Qiangtang terrane on the north side, and the uplift in central. The zircon Eu/Eu* results show that the crust in central part of Tibetan plateau thickened by ∼20 km in Paleogene, resulting in ∼3 km surface uplift. Sediments created a total of about 1 km of surface uplift throughout the Paleogene, and the deposition rate began to slow down significantly at ∼40 Ma. Therefore, it is inferred that in the early Cenozoic, the uplift of the valley was mainly caused by sedimentation. With the continuous downward subduction of the Indian plate, at about 40 Ma, factors such as crustal shortening dominated the uplift of the central valley, and the uplift caused by deposition only accounted for a very small part. In general, the uplift of the Central Valley in the Paleogene was mainly affected by crustal shortening, but a quarter of the surface uplift was caused by the accumulation of sediments.

Mapping specific groundwater nitrate concentrations from spatial data using machine learning: A case study of chongqing, China

Groundwater resources is not only important essential water resources but also imperative connectors within the intricate framework of the ecological environment. High nitrate concentrations in groundwater can exerting adverse impacts on human health. It is imperative to accurately delineate the distribution characteristics of groundwater nitrate concentrations. Four different machine learning models (Gradient Boosting Regression (GB), Random Forest Regression (RF), Extreme Gradient Boosting Regression (XG) and Adaptive Boosting Regression (AD)) which combine spatial environmental data and different radius contributing area was developed to predict the distribution of nitrate concentration in groundwater. The models use 595 groundwater samples and included topography, remote sensing, hydrogeological and hydrological, climate, nitrate input, and socio-economic predictor. Gradient Boosting Regression model outperforms the other models (R2 = 0.627, MAE = 0.529, RMSE = 0.705, PICP = 0.924 for test dataset) under 500 m radius contributing area. A high-resolution (1 km) groundwater nitrate concentration distribution map reveal in the majority of the study area, groundwater nitrate concentrations are below 1 mg/L and high nitrate concentration (>10 mg/L) proportion in southeast, northeast and central main urban area karst valley regions is 1.89%, 0.91%, and 0.38% respectively. In study area, hydrogeological conditions, soil parameters, nitrogen input factors, and percentage of arable land are among the most influential explanatory factors. This work, serving as the inaugural application of utilizing effective spatial methods for predicting groundwater nitrate concentrations in Chongqing city, furnish decision-making support for the prevention and control of groundwater pollution, particularly in areas primarily dependent on groundwater for water supply and holds profound significance as a milestone achievement.

Vulnerability of household livelihoods to climate variability and change in the central rift valley sub-basin of Ethiopia

Ethiopia, despite contributing minimally to global greenhouse gas emissions, is consistently cited as one of the most vulnerable countries, not only in Sub-Saharan Africa regions but also globally, to climate variability and change. The country's farming households are most vulnerable because of their climate-sensitive livelihoods and limited resources to finance adaptation measures. This study aimed to assess the livelihood vulnerability of communities reliant on a mixed crop-livestock agricultural system and natural resources in the Central Rift Valley sub-basin of Ethiopia to climate variability and change. Structured interviews were used to collect quantitative data from 339 randomly selected households. Livelihood Vulnerability Index was developed to assess the degree of livelihood vulnerability between the two districts. The survey results were supported and substantiated by focus group discussions. The findings show that farm households living in the sub-basin experience different levels of vulnerability to climate variability and change because of their varying adaptive capacities. Considering the aggregate Livelihood Vulnerability Index, Arsi Negele district is considered to be more vulnerable to climate variability and change. The livelihood Vulnerability Index-Intergovernmental Panel on Climate Change results also show that Arsi Negele is more vulnerable since its exposure scores exceed its adaptive capacity. Several factors contribute to the weak adaptive capacity of farmers in Arsi Negele. These factors include lesser adoption of agricultural technology, a low level of knowledge and education, insufficient social networks, less diversification of livelihood strategies, and higher socio-demographic vulnerability. In contrast, Adami Tullu Jido Kombolcha district has a higher sensitivity score due to its limited access to potable water, housing, and land ownership. Strategies that minimize households' degree of sensitivity and enhance their adaptive capacity should be promoted. Such strategies should include the adoption of improved agricultural technologies, strengthening awareness and technical capacity, promoting better soil and water management, accessing credit options, and building community networks. Diversifying household income and establishing alternative livelihoods should also be encouraged.

Climate and human activities impact on runoff and sediment yield in the central rift valley of Ethiopia

Climate and human activities impact on runoff and sediment yield in the central rift valley of Ethiopia

Growth, Yield and Economic Advantage of Onion (Allium cepa L.) Varieties in Response to NPSB Fertilizer and Planting Pattern

Haphazard and low soil fertility, low yielding verities and poor agronomic practices are among the major factors constraining onion production in the central rift valley of Ethiopia. Therefore, a field experiment was conducted in East Showa Zone of Adami Tulu Jido Combolcha district in central rift valley areas at ziway from October 2021 to April 2022 to identify appropriate rate of NPSB fertilizer and planting pattern of onion varieties. The experiment was laid out in split plot design of factorial arrangement in three replications. The main effect of NPSB blended fertilizer rates and varieties (red coach and red king) significantly (p<0.01) influenced plant height, leaf length, leaf diameter, leaf number and fresh leaf weight, shoot dry matter per plant, and harvest index. Total dry biomass, bulb diameter, neck diameter, average fresh bulb weight, bulb dry matter, marketable bulb yield, and total bulb yield were significantly (p<0.01) influenced only by the main effect of NPSB blended fertilizer rates. In addition, unmarketable bulb yield was statistically significantly affected (p≥0.05) by the blended fertilizer rates and planting pattern. Moreover, days to 90% maturity of onion was affected by the main factor of NPSB fertilizer rate, variety and planting pattern. The non-fertilized plants in the control treatment were inferior in all parameters except unmarketable bulb yield and harvest index. Significantly higher marketable bulb yield (41 t ha-1) and total bulb yield (41.33 t ha-1) was recorded from 300 kg ha-1 NPSB blended fertilizer rate applied. Double row planting method and hybrid red coach onion variety had also gave higher growth and yields. The study revealed that the highest net benefit of Birr, 878,894 with lest cost of Birr 148,006 by the combinations of 150 kg blended NPSB ha-1 with double row planting method (40cm*20cm*7cm) and red coach variety which can be recommendable for higher marketable bulb yield and economic return of hybrid onion for small scale farmers in the study area. Also, for resource full producers (investors), highest net benefit of Birr 1,205,372 with higher cost (159,628 Birr) by application of 300 kg NPSB ha-1 is recommended as a second option. However, the research should be replicated both in season and areas to more verify the recommendations.

Dynamics of Spatiotemporal Variation of Groundwater Arsenic in Central Rift Vally of Ethiopia: A Serial Cross-Sectional Study.

Arsenic is a well-known, highly poisonous metalloid that affects human health and ecosystems and is widely distributed in the environment. Nevertheless, data on the spatiotemporal distribution of arsenic in groundwater sources in Ethiopia are scarce. The principal aim of this study was to assess the extent of arsenic in groundwater sources and analyze the spatiotemporal variations in the central rift valley of Ethiopia. The study employed a serial cross-sectional study design and census sampling methods. The concentrations of arsenic in the groundwater samples were determined using inductively coupled plasma mass spectrometry (ICP-MS) at the Ethiopian Food and Drug Authority laboratory. Descriptive statistical analyses were performed using IBM SPSS version 29 software. Additionally, ArcGIS software was utilized to map the spatiotemporal distribution of arsenic. Furthermore, Minitab statistical software version 21.4 was employed to assess the correlation between spatiotemporal variations of arsenic concentrations in groundwater sources. The mean values of arsenic in the groundwater samples were 11.2 µg/L during the dry season and 10.7 µg/L during the rainy season. The study results showed that 18 wells (42.2%) and 22 wells (48.8%) had higher arsenic concentrations (>10 µg/L) during the dry and rainy seasons, respectively. Thus, arsenic levels in 42.2% and 48.8% of the samples exceeded the maximum threshold limit set by WHO, USEPA, and Ethiopian standards (10 µg/L), respectively, during the dry and rainy seasons. Furthermore, our analysis revealed a significant positive correlation between arsenic in groundwater and well depth (r = .75, P < .001), indicating a strong association between higher arsenic concentrations and deeper wells. Similarly, we observed a substantial positive correlation between arsenic concentration in groundwater and season (r = .9, P < .001), suggesting notable variations in arsenic levels between dry and rainy seasons. The majority of the groundwater sources in the studied area are unfit for human consumption because they contain high amounts of arsenic, which poses a significant risk to human health. Moreover, the arsenic concentration varied spatially and temporally. Therefore, special attention is needed to reduce arsenic exposure and associated health risks.

Appraising groundwater quality and probabilistic human health risks from fluoride-enriched groundwater using the pollution index of groundwater (PIG) and GIS: a case study of adama town and its vicinities in the central main Ethiopian rift valley.

This research's main objective is to identify the level of contamination in drinking water in Adama town and its environs by employing PIG, GIS and HHRA. The physical-chemical parameters of groundwater were determined, and the results were compared to regional and global drinking water quality guidelines. The pH of groundwater is alkaline, and the contents of Ca2+, Na+, HCO3 -, and F- in the majority of samples surpassed the permissible drinking limit. The hydrochemical facies were identified in the following order: Ca-Mg-HCO3, Na-Ca-HCO3, and Na-HCO3. Cation exchange and Rock-water interaction are the major dominant natural mechanisms controlling groundwater chemistry. Using IDW interpolation methods with Arc GIS 10.8, spatial analysis of the physico-geochemical content of water divulged that TDS, pH, TH, EC, Mg2+, Ca2+, K+, Na+, Cl-, HCO3 -, F-, and SO4 2- all exhibit a positive trend in the direction of groundwater flow from the upland to the lowland (rift floor). As per PIG, the results show that 57%, 33%, 7% and 3% of the samples were found in the insignificant, low, moderate and high, correspondingly. The total hazard index (THI) is calculated from hazard quotients (HQIntake and HQDermal) results showing 83%, 73%, and 57% of the samples exceed the non-carcinogenic health threat of fluoride THI >1 in drinking water for children, women and men. Children are more susceptible to danger than either males or women, according to the THI data, based on body weights and consumption rates. Similarly, females are also more vulnerable to health risks than men.

Evaluation of surface runoff and sedimentation into the Lake Ziway from selected land cover types, central rift valley of Ethiopia

Study regionLake Ziway watershed, Central rift valley of Ethiopia Study focusLake Ziway is currently under huge threat of sediment deposition and water consumption from the upper stream areas of the watershed. The objective of this study was to quantify the sediment and runoff contribution of different land cover types in the Lake Ziway watershed. The study has selected three sites systematically in the lower part of the watershed. Within a site, four land cover types that share similar biophysical characteristics were selected for installing runoff plots with the size of 43.3 m2. The rainfall, runoff and sediment samples collected twice a day from each runoff plot. The composite samples filtered by applying 10 % HCL and the extracted sediment dried in oven at 105°C for 24 h. The dried sediment weighed and computed for each land cover types. New hydrological insights for the regionThe surface runoff from cultivated land is significantly higher than the remaining three land cover types. The total surface runoff in the first and second year from cultivated land is 1033.5 mm and 685.5 mm respectively. The sediment contributed from grassland is significantly lower than the remaining three land cover types. The maximum daily sediment loss per hectare from cultivated land is 84.05 kg and 22.67 kg in the first year and second year respectively. The average annual sediment loss from each land cover types are 5.1, 1.1, 0.9 & 0.5 ton/ha for cultivated land, degraded land, grassland and forestland respectively in the first year. There is moderate linear relationship between surface runoff and rainfall across each land cover. The relationship between the surface runoff and sediment loss is positive and linear. The major source of sediment to the Lake Ziway is from the cultivated land, whereas the least sediment source is from forestland of the watershed. The sediment contribution from cultivated land to the lake should be the priority site for conservation planning of the lake and the entire watershed.

Occurrence and molecular characterization of Potyvirus present in the garlic crop in the Mediterranean ecosystem of the central valley of Chile

Occurrence and molecular characterization of Potyvirus present in the garlic crop in the Mediterranean ecosystem of the central valley of Chile