Upstream Stations Research Articles

Spatio-seasonal variations in water quality status of Migori River in Kenya and associated household health risk implications: an application of a multidimensional water quality index approach

ABSTRACT Water quality monitoring is imperative in providing the objective evidence required to make sound decisions about water quality management. This study aimed to examine the water quality status of the Migori River by determining spatio-seasonal variations in water quality parameters, along with associated influencing factors and potential health risks. Therefore, eighteen physico-chemical and bacteriological variables were sampled and analyzed monthly for six months covering the wet and dry seasons from the upstream, midstream, and downstream stations, and a health risk survey was conducted with 90 watershed households. ANOVA and T-test were used to test for the significant spatial and seasonal variations (p < 0.05), respectively; whereas Pearson's correlation was used to identify relationships between parameters. Hierarchical Cluster Analysis (HCA) and Principal Component Analysis (PCA) were used to find various spatial patterns in the river water quality datasets, while the Canadian Council of Ministries of the Environment Water Quality Index (CCME-WQI) showed the suitability status of the river water quality. The assessed variables showed significant seasonal variability but no significant spatial differences in the river. HCA generated 3 clusters suggesting that water quality deteriorated downstream from the upstream of the watershed. The PCA extracted four PCs explaining 80.5% of the total variance, which suggested that the variations in water quality are attributed to point and nonpoint sources of pollution. While most of the physico-chemical variables were within maximum permissible limits, the bacteriological levels exceeded the prescribed standards. The index ranked the river's water condition between ‘poor’ to ‘marginal’; upstream has better water condition that gradually decreases toward the downstream, and water quality is better in the wet season than the dry season. The study revealed that the water of the Migori River is polluted and potentially hazardous for human usage, and thus suitable pollution control measures are urgently needed to safeguard public health.

Longitudinal fish species diversity and distribution in a medium-sized Afro-tropical river in the Lake Victoria Basin

Despite significantly influencing fisheries characteristics of major global basins, medium-sized rivers such as Awach Kibuon remain the least studied. This study evaluated longitudinal fish species diversity, distribution, and environmental influence in Awach Kibuon River, Lake Victoria Basin, Kenya, to inform sustainable management of fisheries resources within the region. Nine sites located in different zones of the river were sampled monthly for eight months in 2019 and 2020. Fish samples were collected for 45 minutes using a backpack electrofisher on a 50-m river reach in every sampling site. Selected physico-chemical parameters (pH, total dissolved solids (TDS), dissolved oxygen (DO), temperature, conductivity, and turbidity) were measured in situ using standard methods. Longitudinal river fish diversity was assessed using species richness, Simpson's Index (D), Shannon-Weiner Index (H′), and Pielou's Evenness Index (J). A total of 983 fish specimens belonging to 21 species, 12 genera, seven families, and six orders were caught during sampling. Cyprinidae was the most dominant family, represented by nine species, followed by Claridae, Mochokidae, and Cichlidae, represented by three species each. Longitudinal species richness, abundance, and diversity indices deviated from the expected downstream increase. Upstream stations had no fish, whereas midstream and river mouth stations had moderate and high species diversity, respectively. Pearson's correlation analyses showed that temperature, conductivity, TDS, depth, and velocity influenced fish species richness in the river. The above findings call for the inclusion of medium-sized rivers in fisheries management plans of Great Lakes Basins for sustainability.

Impacts of dike systems on hydrological regime in Vietnamese Mekong Delta

Abstract This paper examines the impact of the dike systems on river flows in the Vietnamese Mekong Delta (VMD). The study combined a hydrological change index method and the Mann–Kendall test to assess the temporal dynamics of both discharge and water levels along the main rivers of the VMD. Results highlight that the system of rivers and canals helps facilitate waterway traffic and drainage during the flood season. However, the low elevation of the delta has created conditions suitable for saline water to increasingly penetrate upstream during the dry season. Observed changes in the hydrological indicators at the upstream stations of Tan Chau (Mekong River) and Chau Doc (Bassac River) are not only due to the dike system but also upstream alterations to the flow regime. More research is needed to consider the various drivers of flow-regime change associated with natural and human activities both inside and outside of the study area.

Structure and trophic organisation of the macrobenthic community of the Hassar stream after installation of the Mediouna wastewater treatment plant (Casablanca, Morocco)

The goal of this research is to assess changes in the structure of benthic macroinvertebrate Functional Feeding Groups (FFGs) in the Hassar Stream (north-east of Casablanca) after the Mediouna wastewater treatment plant (WWTP) was installed. Over the course of a year, from November 2013 to October 2014, data on water quality and macroinvertebrate fauna are gathered at seven sampling stations. To measure the resilience of FFGs, macroinvertebrates are used to analyse the influence of physicochemical water quality on their organisation. Based on FFGs abundance, Collector-gatherers make up 39.06 percent of the macroinvertebrates’ assemblage, followed by shredders (28.41 percent) and collector-filters (28.41 percent) (18.76 percent). Except for the upstream stations (S1 and S2), the FFGs ratios indicated that the environment is largely heterotrophic, has a significant relationship with riparian inputs, and generally stable substrates. These findings emphasise the necessity of researching macroinvertebrate FFGs as a supplement to measuring the ecological integrity and resilience of rivers after anthropogenic impact reduction.

Water quality cartography of the upstream part of the Oum Er Rabia hydraulic basin (Morocco)

Water resources constitute the basis of human existence; however, they are becoming increasingly scarce under conditions of population increase, economic development, climate change and especially the impact of pollution due to human activities such as the discharge of wastewater without treatment in rivers, lakes … Also, in Morocco, water resources are becoming scarce as in the global what makes this country among the areas under water stress. The main objective of this study is the evaluation of the water quality of the upper part of Oum Er Rabia. The results of bacteriological analyzes from the various stations showed an increase in total coliforms and feacal coliforms downstream of the Khenifra wastewater treatment plant and at the upstream station of the El Hansali dam. Regarding the physicochemical quality, the water of the majority of the controlled stations is of average to poor quality except one station which has a very poor quality according to the Moroccan standard relating to surface water.

Spatial water quality assessment of a mountain stream in northwestern India using multivariate statistical techniques.

The water quality of Himalayan rivers and streams is deteriorating due to multitude of anthropogenic and natural influences and the changes are more pronounced in smaller hill basins with high human influx. Inadequate data and lack of monitoring further exacerbate the situation. The surface water quality of one such hill stream, Neeru was evaluated for potability and irrigation quality. The water quality parameters were analysed at 25 sampling stations over a stretch of 30km across four seasons during a 2-year study from January 2014 to December 2015. The CCME Water Quality Index (WQI) indicated excellent water quality in upstream stations, while the midstream and a few downstream stations revealed varying degrees of impaired water quality. Although the irrigation quality of the stream was excellent, pollution levels near urban areas were rather high, necessitating considerable treatment for human consumption. The factor analysis yielded seven components with Eigenvalues greater than one that accounted for 83.656% of the variance and enabled the grouping of selected parameters based on comparable characteristics. The hydrogeochemical characteristics of the water samples indicated that they lie within the zone of rock dominance, while the trilinear diagram depicted the Ca-bicarbonaterich stream water. The study concluded that the upstream stations revealed pristine water quality, which significantly degraded towards human settlements. It thus calls for regular and long-term monitoring of the surface water quality to ensure the continuous and sustainable use of this important water body.

Dynamic multivariate analysis for pollution assessment and river habitat conservation in the Vietnamese La Buong watershed.

Analysis of temporal patterns of high-dimensional time-series water quality data is essential for pollution management worldwide. This study has applied dynamic factor analysis (DFA) and cluster analysis (CA) to analyze time-series water quality data monitored at the five stations installed along the La Buong river in Southern Vietnam. Application of the DFA identified two types of temporal patterns, one of the run-off driven parameters (total suspended solid (TSS), turbidity, and iron) and the other of diffuse source pollution. The association of the variables like BOD5 and COD at most stations to the run-off-driven parameters revealed their sharing of drivers. On the contrary, separating variables like phosphate (PO43) at the three upstream stations from the run-off patterns suggested their local point-source origin. The DFA-derived factors were later used in the time-point CA to explore the seasonality of water quality parameters and their pollution intensities compared to regulatory levels. The result suggested intensification in wet season of Fe, TSS, BOD5, and COD concentrations at most sites, which are unobservable in run-off detached parameters like reactive nitrogen, phosphate (PO43-), and E. coli. These findings generated robust insights to support water quality management for river habitat conservation.

Hybrid metaheuristic machine learning approach for water level prediction: A case study in Dongting Lake

A reliable water level prediction in a lake system is crucial for water resources management, flood control, etc. The objective of this study is to propose a machine learning model which is able to achieve a considerably high level of accuracy in terms of water level prediction. Dongting Lake, which is the second-largest freshwater lake system in China, was selected as the study area. The hourly water level, flow rate, rainfall and temperature of the upstream water stations and rainfall of the downstream water stations were used as the input features, to predict the water level at the downstream stations. Multilayer perceptron neural network (MLP-NN), Elman neural network (ENN), and integration of particle swarm optimisation algorithm to Elman neural network (PSO-ENN) were selected as the model development techniques. The PSO-ENN model appears as the best performed model, as it records NSE of 0.929–0.988, RMSE of 0.129–0.322 and MAE of 0.151–0.359 at the downstream stations in Dongting Lake. The PSO-ENN model also shows its ability to provide better performance for the water level prediction of 36 h in advance. In terms of input variables sensitivity, the developed model is most sensitive to flow rate, followed by rainfall.

Copula-Based Multivariate Simulation Approach for Flood Risk Transfer of Multi-Reservoirs in the Weihe River, China

The interplay of multi-reservoirs is critical in reservoir joint disposal and water conservancy projects. As the flood risk of upstream hydrological stations could be transferred and unevenly distributed to downstream tributary stations, flood risk transfer through multi-reservoirs warrants further investigation. This study proposed a copula simulation approach to develop a joint flood risk distribution of multi-reservoirs (spanning Xianyang, Huaxian County, and Zhangjiashan) in a drainage tributary of the Weihe River. Pair-copulas of each reservoir pair were constructed to analyse the correlations between the reservoir sites. The approach was then used to create a joint flood risk distribution for the reservoirs. The flood risk and corresponding flood volume of Zhangjiashan were calculated based on the flood risk levels of Xianyang and Huaxian County. The results indicate that the flood risks of Huaxian County would be transferred to Xianyang and Zhangjiashan to some extent, and Xianyang could mitigate more flood risks from Huaxian County than from Zhangjiashan. The findings have significance for informed decision-making regarding the Zhangjiashan reservoir construction project.

Morphological analysis and evaluation of Givi-chay River conduit form (northwest of Iran)

Abstract In this study, the factors affecting the formation of channel patterns and dynamics in the Givi-chay River during the period 2019–2000 were analysed. To evaluate the river strength, flaw stress and its effects on channel morphology, Landsat 7 and 8 images, topographic maps, geology, and hydrological and field data were used. According to the results of the calculation of hydrological indicators, in terms of 15, the index, a significant difference is seen among upstream and downstream stations. Therefore, it can be found that the presence of the Givi Dam has created a good platform for intensifying the hydrological and morphological changes of the river plan. The particular strength of the river in all parts of the fourth interval and the ninth, 12th, eighth (second interval) levels causes the erosion threshold to soar. The highest amount of shear stress was observed in the second interval at 12, 13, and 9, respectively. Generally, the changes of the Givi River Plan include expansion of existing meanders, displacement of paths, increase of curvature and formation of small meanders and formation of channel pattern and dynamics, affected by discharge provision, sediment discharge due to dam construction, lithological resistance of the riverbed and human interference.

Diversity of zooplankton in Kadalundi-Vallikunnu Community Reserve, North Kerala, India

Zooplankton samples collected from ten stations covering the entire stretch of the Kadalundi-Vallikunnu CommunityReserve, Kerala, south India, for a period from July 2018 to June 2019 were studied. Twenty eight groups of zooplankton viz. copepods, foraminifera, medusae, chaetognaths, siphonophores, ctenophores, ostracods, cladocera, Lucifer sp., amphipods, isopods, appendicularia, Balanus nauplii, cyphonautes larvae, polychaete larvae, echinoderm larvae, ephyra larvae, brachiopod larvae, alima larvae of squilla, aquatic insect larvae, prawn larvae, crab zoea, crab megalopa larvae, bivalve larvae, pteropods, gastropod larvae, fish eggs and fish larvae were recorded. Among these, copepods formed the major portion of 43%. An average of 18330 nos. per 100 m3 was noticed from the study area. The maximum and minimum density of zooplankton was observed at Station 1 and 10 respectively and a decreasing trend in abundance was recorded from barmouth towards upstream stations. Seasonal studies indicated a maximum of 52% during pre-monsoon, followed by 36% during post-monsoon and a minimum of 12% during monsoon. Different indices of diversity, dominance plot, dendrogram and Multi Dimensional Scaling (MDS) plot are presented and discussed. Keywords: Biodiversity, Estuary, PRIMER, Primary consumers, Seasonality

Kemelimpahan anggang-anggang Ptilomera dromas Breddin (Hemiptera: Gerridae) di Sungai Ciliwung dalam kaitannya dengan kualitas air

Anggang-anggang Ptilomera dromas Breddin (Gerridae: Hemiptera) adalah serangga akuatik yang ditemukan di berbagai perairan, seperti sungai, kolam, dan danau. Penelitian ini mengkaji kemelimpahan P. dromas di Sungai Ciliwung dalam kaitannya dengan kualitas air. Kemelimpahan P. dromas disurvei di lima stasiun pengamatan, yaitu stasiun Cilember, Cijulang, Gadog, Katulampa, dan Sempur. Parameter lingkungan yang diukur di setiap stasiun adalah suhu air, suhu udara, pH, arus air, biological oxygen demand (BOD), dissolved oxygen (DO), CO2 bebas, total N, kesadahan air, dan total suspended solid (TSS). Hubungan antara kemelimpahan P. dromas dan parameter lingkungan dianalisis dengan general linier model (GLM). Hasil penelitian menunjukkan bahwa kemelimpahan P. dromas tertinggi terdapat di stasiun Gadog, diikuti oleh Cilember, Katulampa, dan Cijulang. Anggang-anggang P. dromas tidak ditemukan di stasiun Sempur diduga karena adanya penghalang berupa bendung Katulampa dan nilai TSS dan BOD yang tinggi. Berdasarkan analisis GLM, pH dan kesadahan air berpengaruh positif terhadap kemelimpahan P. dromas. Keberadaan P. dromas di stasiun penelitian bagian hulu sungai diduga berkaitan dengan kualitas perairan yang masih baik dan tingkat polusi yang relatif rendah.

Temporal and spatial variation in water quality in the Yangtze Estuary from 2012 to 2018.

Water quality plays an important role in estuarine habitats and affects aquatic organisms. The focus of this study was to understand the temporal-spatial variation of water quality and reveal the natural and anthropogenic drivers by using multiple analysis approaches. Herein, during 2012-2018, six water quality constituents (pH, electrical conductivity (EC), dissolved oxygen (DO), ammonia nitrogen (NH3N), total nitrogen (TN), and total phosphorus (TP) were examined for eight sites in the Yangtze Estuary, and the hydro-sediment data, i.e., discharge (Q) and sediment transport rate (STR), was collected from the upstream hydrological station Datong. The cluster analysis (CA), principal component analysis (PCA)/factor analysis (FA), Canadian Council of Ministers of the Environment Water Quality Index (CCME-WQI), and the Mann-Kendall (MK) test were applied. The eight sampling sites were geographically grouped into cluster I, cluster II, and cluster III based on the characteristics of water quality changes, which are under the influence of the upstream runoff, the anthropogenic activities, and seawater. The results are as follows: (1) NH3N, TN, and DO were key constituents representing the water quality of cluster I and cluster III, and those were EC, TN, and DO for cluster II; (2) The monthly-average Q and STR of Datong were negatively correlated to water quality constituents with seasonal variation except for pH; (3) The impact of anthropogenic activities on water quality was especially reflected in cluster III which is close to the Huangpu River Estuary; upstream runoff was the natural driver of water quality changes for cluster I while that was seawater for cluster II. Seawater acts a key role in affecting the water quality of cluster II situated at the North Branch. Revealing the key drivers of water quality change in the Yangtze Estuary provides a reference for water quality management.

A Bayesian Hierarchical Framework for Postprocessing Daily Streamflow Simulations across a River Network

Abstract Despite the potential and increasing interest in physically based hydrological models for streamflow forecasting applications, they are constrained in terms of agility to generate ensembles. Hence, we develop and test a Bayesian hierarchical model (BHM) to postprocess physically based hydrologic model simulations at multiple sites on a river network, with the aim to generate probabilistic information (i.e., ensembles) and improve raw model skill. We apply our BHM framework to daily summer (July–August) streamflow simulations at five stations located in the Narmada River basin in central India, forcing the Variable Infiltration Capacity (VIC) model with observed rainfall. In this approach, daily observed streamflow at each station is modeled with a conditionally independent probability density function with time varying distribution parameters, which are modeled as a linear function of potential covariates that include VIC outputs and meteorological variables. Using suitable priors on the parameters, posterior parameters and predictive posterior distributions—and thus ensembles—of daily streamflow are obtained. The best BHM model considers a gamma distribution and uses VIC streamflow and a nonlinear covariate formulated as the product of VIC streamflow and 2-day precipitation spatially averaged across the area between the current and upstream station. The second covariate enables correcting the time delay in flow peaks and nonsystematic biases in VIC streamflow. The results show that the BHM postprocessor increases probabilistic skill in 60% compared to raw VIC simulations, providing reliable ensembles for most sites. This modeling approach can be extended to combine forecasts from multiple sources and provide skillful multimodel ensemble forecasts.

Response of runoff components to climate change in the source‐region of the Yellow River on the Tibetan plateau

AbstractClimate change will likely increase the total streamflow in most headwaters on the Tibetan Plateau in the next decades, yet the response of runoff components to climate change and permafrost thaw remain largely uncertain. Here, we investigate the changes in runoff components under a changing climate, based on a high‐resolution cryosphere‐hydrology model (Spatial Processes in Hydrology model, SPHY) and multi‐decadal streamflow observations at the upstream (Jimai) and downstream stations (Maqu and Tangnaihai) in the source‐region of the Yellow River (SYR). We find that rainfall flow dominates the runoff regime in SYR (contributions of 48%–56%), followed by snowmelt flow (contributions of 26%/23% at Maqu/Tangnaihai). Baseflow is more important at Jimai (32%) than at the the downstream stations (21%–23%). Glacier meltwater from the Anyê Maqên and Bayankala Mountains contributes negligibly to the downstream total runoff. With increasing temperature and precipitation, the increase in total runoff is smaller in the warm and wet downstream stations than in the cold and dry upstream station. This is because of a higher increase in evapotranspiration and a larger reduction in snowmelt flow in the downstream region in response to a warming climate. With temperature increase, there is less increase in rainfall flow in the downstream region due to increased water loss through evapotranspiration. Meanwhile, the decline in snowmelt flow is larger further downstream, which can negatively impact the spring irrigation for the whole Yellow River basin that supports the livelihoods of 140 million people. Importantly, we find that baseflow plays an increasingly important role in the permafrost‐dominated upstream region with atmospheric warming and permafrost thaw, accompanied by decreased surface flow. These findings improve our current understanding of how different hydrological processes respond to climate change and provide insights for optimizing hydropower and irrigation systems in the entire Yellow River basin under a rapidly changing climate.

Integrated Hydrologic-Hydrodynamic Inundation Modeling in a Groundwater Dependent Tropical Floodplain

The rapid development of free and open-access hydrological models and coupling framework tools continues to present more opportunities for coupled model development for improved assessment of floodplain hydrology. In this study, we set up an Upper Zambezi hydrological model and a fully spatially hydrological-hydrodynamic coupled model for the Barotse Floodplain using GLOFRIM (GLObally applicable computational FRamework for Integrated hydrological–hydrodynamic Modelling). The hydrological and hydrodynamic models used are WFLOW and LISFLOOD-FP, respectively. The simulated flows generated by the wflow model for the upstream gauge stations before the Barotse Floodplain were quite similar and closely matched the observed flow as indicated by the evaluation statistics; Chavuma, nse = 0.738; kge = 0.738; pbias = 2.561 and RSR = 0.511; Watopa, nse = 0.684; kge = 0.816; pbias = 10.577 and RSR = 0.557; and Lukulu, nse = 0.736; kge = 0.795; pbias = 10.437 and RSR = 0.509. However, even though the wflow hydrological model was able to simulate the upstream hydrology very well, the results at the floodplain outlet gauge stations did not quite match the observed monthly flows at Senanga gauge station as indicated by the evaluation statistics: nse = 0.132; kge = 0.509; pbias = 37.740 and RSR = 0.9233. This is mainly because the representation of both floodplain channel hydrodynamics and vertical hydrological processes is necessary to correctly capture floodplain dynamics. Thus, the need for an approach that saves as a basis for developing fully spatially distributed coupled hydrodynamic and hydraulic models’ assessments for groundwater dependent tropical floodplains such as the Barotse floodplain, in closing the gap between hydrology and hydrodynamics in floodplain assessments. A fully coupled model has the potential to be used in implementing adaptive wetland management strategies for water resources allocation, environmental flow (eflows), flood control, land use and climate change impact assessments. Doi: 10.28991/HEF-2022-03-02-09 Full Text: PDF

Influence of Source Apportionment of PAHs Occurrence in Aquatic Suspended Particulate Matter at a Typical Post-Industrial City: A Case Study of Freiberger Mulde River

Polycyclic aromatic hydrocarbons (PAHs) have received extensive attention because of their widespread presence in various environmental media and their high environmental toxicity. Thus, figuring out the long-term variances of their occurrence and driving force in the environment is helpful for environmental pollution control. This study investigates the concentration levels, spatial variance, and source apportionment of PAHs in suspended particulate matter of Freiberger Mulde river, Germany. Results show that the concentrations of the 16 priority PAHs suggested by USEPA (Σ16PAHs) were in the range of 707.0–17,243.0 μg kg−1 with a mean value of 5258.0 ± 2569.2 μg kg−1 from 2002 to 2016. The relatively high average concentrations of Σ16PAHs were found in the midstream and upstream stations of the given river (7297.5 and 6096.9 μg kg−1 in Halsbrucke and Hilbersdorf, respectively). In addition, the annual average concentration of Σ16PAHs showed an obvious decreasing pattern with time. Positive Matrix Factorization (PMF) receptor model identified three potential sources: coke ovens (7.6–23.0%), vehicle emissions (35.9–47.7%), and coal and wood combustion (34.5–47.3%). The source intensity variation and wavelet coherence analysis indicated that the use of clean energy played a key role in reducing PAHs pollution levels in suspended sediments. The risk assessment of ecosystem and human health suggested that the Σ16PAHs in the given area posed a non-negligible threat to aquatic organisms and humans. The data provided herein could assist the subsequent management of PAHs in the aquatic environment.

CORRELATING STREAM GAUGING STATIONS USING ARTIFICIAL NEURAL NETWORKS

The present work aims at correlating stream gauging stations along river Krishna of the state of Maharashtra, India using Artificial Neural Networks. For this ANN models were developed with stream flow at the upstream stations(s) as inputs and stream flow at the downstream station as output. All the models show excellent results and prove the ability of ANNs to offer solutions with limited amount of data. The models will be useful to develop a decision support system for the downstream locations especially in case of flood events.

From freshwaters to bivalves: Microplastic distribution along the Saint-Lawrence river-to-sea continuum

Despite the close connection of freshwaters to human health, the occurrence and fate of microplastics in marine estuaries remain poorly documented. To study these particles in the Saint-Lawrence River (Quebec, Canada), surface water and marine bivalve samples were collected along the river-to-sea continuum. The water samples were subdivided to characterize the large microplastics (LMPs; 300–3200 µm) and the small microplastics (SMPs; 20–300 µm). Particles were identified by microscopy and infrared spectroscopy techniques. The concentration of LMPs was higher in the surface water in the downstream stations (0.0319 ± 0.0147 items.L-1) compared to the upstream stations (0.0007 ± 0.0006 items.L-1). No clear trend was observed for the SMPs. After digestion of the biological tissues, the microplastics ingested by the bivalves were recovered and characterized by microscopy coupled with infrared spectroscopy. Up to 3 items were found per bivalve suggesting that these particles are also present in the water column of the marine estuary and the gulf. The physico-chemical gradients along the continuum were monitored since they could be directly involved in the vertical and horizontal transport of microplastics. This study provides scarce field data collected along the world’s largest estuary and gives new insights concerning the fate of microplastics along a river-to-sea continuum.

Keanekaragaman Mikroalga sebagai Bioindikator di Perairan Sungai

This study aims to determine the diversity of microalgae and their relationship with water quality in the Air Lais River. The method used is a survey method. The results showed that there were 28 species of microalgae consisting of 7 divisions. The abundance of microalgae at the upstream station was 52 ind/ml, the middle station was 50 ind/ml and the downstream station was 115 ind/ml. The microalgae diversity index at each station was 2.2; 2.2; and 2.59, with a moderate level of diversity criteria. The microalgae dominance index was in the low dominance criteria, with the value of each station being 0.21; 0.20; and 0.14. In conclusion, the condition of the Air Lais River is still relatively clean and shows a normal tolerance range for microalgae life.&#x0D; Keywords: Diversity, Microalgae, Lais Water River