Ecohydraulic Model Research Articles

Evaluation of the highly sinuous bend sequences using an ecohydraulic model to ascertain the suitability of fish habitats for river ecological conservation

The spatial and temporal patterns of river meanders play a crucial role not only in shaping the hydrogeomorphic properties of channels and floodplains but also in ascertaining the suitability of fish habitats for river ecological conservation. This study evaluates hydrodynamic features and fish habitat quality in six highly sinuous bend sequences along the Black River in China’s Qinghai plateau. The ecohydraulic model system was used to simulate hydrodynamics, habitat suitability, and sediment transport to determine the habitat quality of the highly sinuous bend sequences. The results have successfully identified differences in the suitability of various bends for fish spawning. Bend 1 was found to be the most suitable among all bends, while bends 5 and 6 were deemed unsuitable specifically during higher flood flows. Cases 3 and 4 were discovered to be highly suitable for fish habitat under normal discharge scenarios. Conversely, cases 5 and 6 were the least suitable, with cases 5 and 6 exhibiting the worst habitat quality, with HSI values nearing zero under high discharge. The study concluded that regulated discharge conditions could support fish spawning in these sinuous bends, with lower flood flows promoting habitat suitability and higher flood flows fragmenting habitat quality. The findings highlight the importance of diverse hydrodynamic and geomorphic conditions in creating suitable fish habitats across varying flow conditions, offering insights into the conservation and management of mountain rivers to protect endangered fish species and aquatic organisms.

Distinctive hydrodynamic properties and ecological responses of multi-thread rivers under different degrees of multiplicity in the Upper Yellow River

Alluvial rivers that exhibit multi-thread patterns are common in nature and can be the dominant channel morphology in large rivers. However, their ecological properties in response to diverse and dynamic channel morphology has gained limited attention and remained poorly understood. In this study, we adopted an eco-hydraulic model by integrating a hydrodynamic, a sediment-transport, and a habitat-suitability model to assess habitat quality for fish species (Schizopygopsis pylzovi and Platypharodon extremus) in three anabranching reaches with each exhibiting a distinct anabranching morphology in the Upper Yellow River, eastern Qinghai-Tibet Plateau. Based on the hydrologic data and actual channel morphology, we modeled the hydrodynamic and sediment-transport conditions for a period spanning ten years, and simulated habitat conditions under a potentially changing environment with different flow magnitudes and frequencies. The results indicated that the average flow velocity in the low and mid-order anabranching reaches is higher than that in the high-order, complex anabranching reaches. Meanwhile, the bedload transport rate was higher in the high and mid-order anabranching reaches than that in the low-order anabranching reach, demonstrating a greater transport efficiency of multi-thread systems with a greater multiplicity. Consequently, the habitat suitability shows a deteriorating trend over the ten-year modeling period and Schizopygopsis pylzovi shows better habitat status than Platypharodon extremus. The flow magnitudes and frequency also have a significant impact on the distribution of high habitat suitability index among the different river patterns in Upper Yellow River. This study can provide valuable information to optimize ecological outcomes and provide valuable insights for future dam operation strategies and consideration efforts aimed at preserving and restoring riverine ecosystems.

Evaluating the physical habitat of riffle‐pool design in support of river habitat protection and rehabilitation

AbstractRiffle‐pool constructions are common practice in river management and fish conservation, but insufficient science exists to guide objective design of riffle‐pool. Understanding the spatial design of a riffle‐pool in river systems has significant value because it can provide important information to ameliorate aquatic species decline. In this study, six types of riffle‐pool structures were designed to assess hydrodynamic and riverbed morphology effects on stream habitat status. A two‐dimensional ecohydraulic model was used to assess the roles of different riffle‐pool designs in river habitat conditions. The natural flow condition and three types of flood flow conditions were applied to the six types of riffle‐pool structures to evaluate the habitat quality and the sustainability of the riffle‐pool design in mountain rivers. The long‐term impacts of the hydrodynamic and hydromorphology conditions on river physical habitat status were also analysed. The results indicate substantial differences in habitat quality among six riffle‐pool structures. It was found that narrow riffle‐pool construction yielded the best performance for the fish habitat, which had the best habitat quality among six riffle‐pool designs with the smallest pool area. In the same riffle‐pool structure, the habitat suitability in the riffle‐pool sequence will primarily increase more rapidly and then decrease gradually along with the discharge increase. Under the flood discharge scenarios, low flood discharge could improve riffle‐pool habitat quality, while high flood discharge could fragment the riffle‐pool habitat quality further. The long‐term hydrodynamic conditions have the same effects on all six cases. Overall, low discharge and smaller pool design would be beneficial to the river system, which could help maintain habitat diversity of mountain rivers. This analysis could provide valuable information for river management and decision‐making, which could assist in designing better mountain river habitats to promote conservation and rehabilitation of endangered biota.

Ecohydraulic modelling to evaluate cascade dam construction impact and support fish habitat restoration

The cascade dam constructions in the Lancang River basin will alter the river's hydrological status and affect the habitat quality of spawning sites. In this study, an ecohydraulic model was proposed to evaluate the effects of the cascade dam construction and support the restoration of spawning sites. Four spawning sites and two fish species were selected as computational domains and target fish species, respectively. The Schizothorax prenanti and Schizothorax davidi represent dominant and protected fish species in all four spawning sites. Typical annual flow discharges were used to represent the flow pattern in the Lancang River. The hydrodynamic parameters and habitat indicators were simulated and used for ecological status evaluation. Three scenarios were proposed: pre-dam construction, after dam construction, and restoration strategies. The results indicated that the quality of the Schizothorax prenanti habitat is better than that of the Schizothorax davidi habitat in all scenarios, with Schizothorax prenanti mainly distributed in the middle of the river and Schizothorax davidi scattered along the riverside. The cascade dam construction will fragment spawning Sites 1 and 2 while it will improve the habitat status in Sites 3 and 4. In addition, with restoration strategies applied, the prediction indicates that the degree of fragmentation of the habitat at spawning Sites 1 and 2 can be significantly reduced. The post-restoration effects also proved the feasibility of these two recommended restoration strategies. The analysis indicated that the investigation of the Lancang River could yield valuable information about hydropower development and habitat protection.

Stocking to offset negative effects of dam construction and balance the ecosystem

AbstractAn ecohydraulic model system was developed to evaluate the effects of the Da‐Wei dam construction and possible fish restoration strategies. The ecohydraulic model system consists of a hydrodynamic model, a hydromorphology model, a habitat model, and the logistic and matrix population models. The effects of dam construction and fish stocking strategy on fish habitat and population status were studied in the Jiao‐Mu River, providing the modeled ecological status of Schizothorax prenanti and Schizothorax plagiostomus heckel populations within the river segment. The two fish species richness, fish age structures, and fish density distributions were predicted. Based on the fish number prediction, the optimal number of fish to stock was evaluated with the population models, and an optimal fish stocking proposition was worked out. The results indicated that the two fish species habitat quality and fish richness would decrease due to the hydropower dam construction, and the fish stocking strategy could make up the fish species ecological status. The findings could facilitate the quantity and quality assessment of a dam development plan and increase the success rate of fish restoration.

A CUDA Fortran GPU-parallelised hydrodynamic tool for high-resolution and long-term eco-hydraulic modelling

Eco-hydraulic models are wide extended tools to assess physical habitat suitability on aquatic environments. Currently, the application of these tools is limited to short river stretches and steady flow simulations. However, this limitation can be overcome with the application of a high-performance computing technique: graphics processing unit (GPU) computing. R-Iber is a GPU-based hydrodynamic code parallelised in CUDA Fortran that, with the integration of a biological module, performs as an eco-hydraulic numerical tool. R-Iber was validated and applied to real cases by using an optimised instream flow incremental methodology in long river reaches and long-term simulations. R-Iber reduces the computation time considerably, reaching speed-ups of two orders of magnitude compared to traditional computing. R-Iber allows for overcoming the current limitations of the eco-hydraulic tools with the simulation of high-resolution numerical models calculated in a reasonable computation timeframe, which provides a better representation of the hydrodynamics and the physical habitat.

Habitat response of adult fish species under the influence of ecological flow and hydrodynamic regime in perennial river system

AbstractThe escalating anthropogenic activities in recent decades are constantly affecting the aquatic ecology and posing a threat to freshwater species. In this study, a two‐dimensional ecohydraulic model and multiple criteria decision analysis (MCDA) coupled framework is employed in the Dikhow River, India, to investigate the favourable habitat condition for the nearly threatened Notopterus chitala fish locally known as Chital fish. The habitat residence suitability and habitat suitability indices are calculated at the observed and ecological flows. The ecological flow rates are computed from flow duration curve shifting and flow duration curve analysis methods. The hydrodynamic computations are carried out using a 1D‐2D coupled MIKE FLOOD model. The habitat assessment of the targeted species is carried out by constructing the suitability curves from the computed hydraulic parameters at different environmental management conditions. Results from the habitat assessment curves indicate that the maximum habitat suitability index is found for the targeted fish species at average annual flow. Based on the MCDA analysis, the outer banks of the meander zones are identified as not suitable residence regions for the target species. This study revealed that the coupled approach could be useful to regulate the stream restoration strategies and identify potential habitat preference locations in the domain.

Effects of forest fires on headwater streamflow and the habitat suitability for benthic macroinvertebrates

ABSTRACT We modelled hydrological, hydraulic and habitat suitability changes in a Mediterranean catchment after a wildfire. Gauged pre/post-fire hourly discharges were used to assess actual pre/post-fire hydrological conditions. To remove the weather variability effect, daily pre/post-fire discharges were simulated under the same weather conditions. An eco-hydraulic model was employed to calculate flow velocities, water depths and macroinvertebrate habitat suitability at various discharges across a 165 m long reach. The fire increased the magnitude and frequency of peak velocities and depths by 6.5–475%. Increased post-fire rainfall exacerbated hydrological-hydraulic extremes. However, the short duration of post-fire extremes led to small impacts on the habitat suitability for macroinvertebrates, which were stressed for a maximum 18.4% of the time after the fire (350 days in five years). In small Mediterranean-climate headwaters, after wildfires, less frequent streamflow becomes more frequent, high and of short duration. Macroinvertebrates largely resist such short-term, low-magnitude hydrological-hydraulic changes.

Ecohydraulic model for designing environmental flows supports recovery of imperilled Murray cod (

Large dryland and semi-arid rivers are among the world’s most heavily modified ecosystems, and the Darling–Baaka River of eastern Australia highlights the challenges in conserving such ecosystems. Since 2000, the hydrology at the downstream end of the system (the Lower Darling River, LDR) has been transformed from a naturally near-perennial flowing system to an intermittent one by increased water abstraction, prolonged drought and climate change. This hydrological change has placed immense pressure on the native fish populations, such as the imperilled Murray cod (Maccullochella peelii), as evidenced by the 2018–19 catastrophic fish kills. Here we outline an ecohydraulic conceptual model for designing environmental flows to support spawning and recruitment of Murray cod. An environmental flow based on this model was released in 2016–17, following 524 consecutive days of continuous zero flows. The LDR flow consisted of an increased discharge in late winter–spring to promote broad-scale lotic (i.e. >0.3 m s–1) conditions, hydraulic complexity and continuous base flows to maintain connectivity and water quality. Monitoring of Murray cod during and following the flow revealed successful spawning and recruitment. This finding is significant because it provides justification for altering current water management policies that are failing to protect this nationally significant ecosystem.

Environmental Flows as a Proactive Tool to Mitigate the Impacts of Climate Warming on Freshwater Macroinvertebrates

What would happen in Mediterranean rivers and streams if warming but not drying occurred? We examined whether the delivery of environmental flows within a warming climate can maintain suitable macroinvertebrate habitats despite warming. A two-dimensional ecohydraulic model was used to (1) simulate the influence of water temperature and flow on macroinvertebrates by calculating habitat suitability for 12 climate change scenarios and (2) identify the mechanism by which macroinvertebrate assemblages respond to warming. The results suggest that not all watersheds will be equally influenced by warming. The impact of warming depends on the habitat conditions before warming occurs. Watersheds can, thus, be categorized as losing (those in which warming will degrade current optimal thermal habitat conditions) and winning ones (those in which warming will optimize current sub-optimal thermal habitat conditions, until a given thermal limit). Our models indicate that in losing watersheds, the delivery of environmental flows can maintain suitable habitats (and, thus, healthy macroinvertebrate assemblages) for up to 1.8–2.5 °C of warming. In winning watersheds, environmental flows can maintain suitable habitats when thermal conditions are optimal. Environmental flows could, thus, be used as a proactive strategy/tool to mitigate the ecological impacts of warming before more expensive reactive measures within a changing climate become necessary.

Identifying fish ecological risk patterns based on the effects of long-term dam operation schemes

River regulation patterns play a key role in ecohydrology and they directly affect hydrodynamic variables, fish habitats, and fish abundance conditions. In the Kraal River, the Trunk Dam is currently being constructed and very little is known about the dam construction and operation impacts on fish species. In this study, an ecohydraulic model was built and linked to hydromorpho-dynamic, fish habitat, and fish abundance simulations. Two fish species, schizothorax (Schizothorax) and schizothorax (Racoma), representing a main and an endangered fish species, respectively of the Kraal River, were studied; their habitats and abundance statuses were predicted and analyzed based on four different long-term dam operation scenarios. Fish-friendly river regulation scenarios were also examined. The temporal- and spatial-scale hydro-morphodynamic results indicate that the erosion effects are much more significant than the deposition effects. Our study suggests that habitat destruction and fragmentation existed for all presented river regulation scenarios. The analysis indicates that long-term river regulation will result in a decrease in the fish population. However, there will be different levels of decline for fish habitats and populations depending on the dam operation scenarios. This study contributes to a better understanding of the dam-induced temporal habitat fragmentation and response of fish communities. This study also provides quantitative evidence for suitable river regulation scenarios and fish stocking strategies, which can help the fish community recover to a stable level.

Water-energy-ecosystem nexus: Balancing competing interests at a run-of-river hydropower plant coupling a hydrologic–ecohydraulic approach

The water-energy-ecosystem nexus represents a complex interlinkage that depends on the flow regime type. Inadequate environmental flows setting may adversely affect the riverine ecosystem and/or hydropower revenue. This issue was addressed quantitatively in this study by considering a run-of-river hydropower plant located in a river of the Tagus basin characterised by a pluvial winter flow regime. Three models: a hydropower, a hydrologic, and an ecohydraulic model were integrated to estimate the influence of nine hydrologically-based environmental flow methods on hydropower production, flow regime alteration and fish habitat conditions. The target fish species was a native cyprinid fish, the Iberian barbel (Luciobarbus bocagei), considering three life-stages. Results show that high environmental flow releases did not necessarily provide the highest habitat availability and suitability at all seasons and fish life-stages. The adult life-stage resulted in being more vulnerable to water diversion, particularly during Spring season. Shallow-water hydromorphological units suffered the highest habitat loss. Some of the environmental flow methods demonstrated inconsistent results over seasons and fish life-stages by either allowing for higher environmental flow releases whereas highly restricting hydropower production or vice versa. However, results also suggest that combined and dynamic environmental flow methods promoted reasonable hydropower production while inducing less than 50% habitat loss and flow regime alteration, regarding the three life-stages over all seasons. This study contributes to the identification of the relationship between conflicting objectives, such as hydropower production and riverine ecosystem conservation. Also, it provides strategic recommendations on energy-ecosystem regulation for sustainable hydropower operation. This study also highlights the importance of considering seasonal flow discharge variability when analysing the water-energy-ecosystem nexus.

Ecohydraulic model development and application: Evaluating the habitats and population of rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and flannelmouth sucker (Catostomus latipinnis) in Colorado River

Ecohydraulics often requires the use of advanced numerical models and ecological theories, which are used for river and aquatic organism management. In this study, a 2D ecohydraulic model system was proposed and used to evaluate the habitat suitability index, weighted useable areas, overall suitability index, fish population number, and fish population density of Colorado River. The 2D ecohydraulic model system comprised hydrodynamic, hydromorphology, habitat, and population models. Three fish species were selected as target fish, which included rainbow trout (Oncorhynchus mykiss), brown trout (Salmo trutta), and flannelmouth sucker (Catostomus latipinnis). Five computational domains of the Colorado River were selected for the ecohydraulic model. The surveyed fish data from 2000 to 2009 were used to calibrate the model system. Results indicated that the predicted fish number showed a good agreement with the surveyed fish. It is indicated that the rainbow trout and brown trout fish number showed decreasing trends from 2000 to 2009, while flannelmouth sucker showed increasing trend from 2000 to 2009. The proposed approach demonstrates that the ecohydraulic model system can be used to accurately simulate the river habitat quality and population status. The ecohydraulic model can be an efficient tool to improve understanding of the different scenarios and to assistant for multiple fish habitat and population prediction in river system. It can also provide decision-makers with valuable information to optimize their management.

Extending water resources performance metrics to river ecosystems

• 2D hydraulic model outputs summarized into multi-dimensional performance metrics. • Assess reliability, resilience, and vulnerability of suitable ecohydraulic conditions. • Complementary metrics facilitate analysis of human - ecosystem water needs. • Performance varies across water management scenarios and climate conditions. A persistent challenge in integrated water management is the ability to accurately evaluate human and ecological tradeoffs. Two-dimensional (2D) hydraulic models are frequently used to evaluate water management alternatives concerning aquatic species physical habitat needs or preferences. Recent studies have assessed the timing or duration of suitable habitat conditions, but no standardized approach exists to integrate and interpret ecohydraulic model outputs within a water management framework. Such an approach is needed to maximize the information obtained from model outputs and to facilitate communication between river scientists and water managers. This study presents a general framework to aggregate and summarize 2D hydraulic model outputs by adapting the traditional water resources metrics of reliability, resilience, vulnerability, and sustainability. Just as these metrics are typically used to quantify distinct aspects of water resources performance, applying them to ecohydraulic conditions facilitates interpretation of ecological performance and human-ecosystem water management tradeoffs. This paper examines the utility and limitations of the proposed framework and metrics in a simple application to fall-run Chinook salmon in a typical Mediterranean-montane stream.

Incorporating fish habitat requirements of the complete life cycle into ecological flow regime estimation of rivers

AbstractMaintenance of ecological flow regime for aquatic biota is essential to river ecosystem health. To estimate ecological flow, habitat simulation methods have been widely applied because of their combination of hydrological regime and species hydraulic preference. However, few methods are available to provide a flow regime that varies over time due to time‐specific habitat requirements from different target species or from one target species at its different life stages. This paper described a novel approach for evaluating the ecological flow regime that was a time series of discharge considering different life stages of target species. First, an ecohydraulic model that combined multivariable habitat suitability curve of target species with a hydraulic module was developed to establish the relationship between habitat status and hydrological conditions. Then, the habitat connectivity index was adopted to assess the spatial patterns of habitat patches. Finally, the ecological flow regime considering the complete life cycle of target species was derived. The developed approach was applied to the middle reach of Huaihe River, where the flow is highly regulated by dams and sluices. The Chinese bream (Parabramis pekinensis) was chosen as the target species for ecological flow calculation. The ecological flow regime in the Lutaizi was provided for the river management. The study provided a promising method to support ecological friendly operations of hydraulic structures for river ecosystem restoration and management.

Ecohydraulic modelling of anabranching rivers

AbstractIn this paper we provide the first quantitative evidence of the spatial complexity of habitat diversity across the flow regime for locally anabranching channels and their potential increased biodiversity value in comparison to managed single‐thread rivers. Ecohydraulic modelling is used to provide evidence for the potential ecological value of anabranching channels. Hydraulic habitat (biotopes) of an anabranched reach of the River Wear at Wolsingham, UK, is compared with an adjacent artificially straightened single‐thread reach downstream. Two‐dimensional hydraulic modelling was undertaken across the flow regime. Simulated depth and velocity data were used to calculate Froude number index, known to be closely associated with biotope type, allowing biotope maps to be produced for each flow simulation using published Froude number limits. The gross morphology of the anabranched reach appears to be controlling flow hydraulics, creating a complex and diverse biotope distribution at low and intermediate flows. This contrasts markedly with the near uniform biotope pattern modelled for the heavily modified single‐thread reach. As discharge increases the pattern of biotopes altered to reflect a generally higher energy system, interestingly however, a number of low energy biotopes were activated through the anabranched reach as new subchannels became inundated and this process creates valuable refugia for macroinvertebrates and fish, during times of flood. In contrast, these low energy areas were not seen in the straightened single‐thread reach. Model results suggest that anabranched channels have a vital role to play in regulating flood energy on river systems and in creating and maintaining hydraulic habitat diversity.

Evaluation of fish habitat suitability using a coupled ecohydraulic model: Habitat model selection and prediction

AbstractThe selection of an approach to evaluate habitat suitability for a specific fish or life stage has been a matter of concern in habitat quality modelling studies. This study has taken Jinshaia sinensis, a commercially valuable fish endemic to the Jinsha River, China, as the target fish species. One‐ and two‐dimensional hydrodynamic models were coupled and combined with fish habitat models for a middle reach of the Jinsha River. The resulting ecohydraulic model was used to predict the changes in hydrodynamics and spawning habitat suitability that resulted from the operation of an under‐construction reservoir downstream of the study area. The preference function (product, arithmetic mean, geometric mean, and minimum value) and fuzzy logic habitat evaluation methods were compared to predict the spawning habitat suitability of the fish. The model was validated using the numbers of spawning eggs, and the results show that both the arithmetic mean and fuzzy logic method can be used to predict spawning habitat suitability. The model predictions show that the hydrodynamics of the study area would be altered if the impoundment water level exceeded 969 m. During the spawning season, the spawning habitat suitability would increase from April to early June and has little change from early June to July under the impact of the reservoir impoundment. The optimal river discharge rate for fish spawning is ~3,500 m3/s, and this would not change after the reservoir begins operation. This research can benefit other regions that will be affected by planned dams by predicting the impacts of reservoir operation on fish habitat quality, and the results will help decision makers protect the health of rivers and the overall ecosystem.

Ecohydraulic modelling of Nestos River Delta under low flow regimes

The determination of a proper minimum environmental flow in a river basin is one of the most critical components of sustainable water resources management, with hydraulic and habitat modelling being the most advance methods for that analysis. The present study illustrates the ecohydraulic modelling of Nestos River Delta at the deltaic zone of a heavily modified watershed under various low flow scenarios, using the RIVER2D Model. RIVER2D is a two-dimensional, depth averaged hydrodynamic and fish habitat model, widely used in environmental flow assessment studies. A detailed digital model of the river channel and its surrounding area was developed, including all the morphological characteristics of the river channel, as well as its various sandy islets. Field surveys in combination with Digital Elevation Model data were used for the development of the digital terrain used as input to RIVER2D model. Several different steady state hydraulic simulations were conducted under typical low flow conditions, producing water depth and water velocity (direction and magnitude) maps for each discharge scenario, while results were verified with the use of field measurements. In the next step, RIVER2D was used for the fish habitat modelling of the study area, with the application of fish preference curves developed specifically for the study area. Finally, the fish habitat modelling was conducted for four different fish species, divided into two age groups, forced under the same five typical low flow conditions. Results reveal that the ecohydraulic modelling of river basins should be considered as an indispensable component in sustainable water resources management.

Developing a Model to Assess the Potential Impact of TUM Hydropower Turbines on Small River Ecology

Small hydropower is a renewable energy technology that is used for electricity generation worldwide, but still has potential for further development. However, during the installation of small hydropower, the ecological impacts of the power plants need to be thoroughly investigated. In addressing the challenges of energy production and minimizing the environmental impacts of small hydropower installation and operation, this study has applied an ecohydraulic model to investigate river hydrodynamics, hydromorphology, habitat, and the population impacts of small hydropower, and presented the Mum River as a case study. Two scenarios were implemented in this research to simulate the hydrodynamic, sedimentation, habitat, and population status in order to assess the potential effects caused by the TUM plant. At the Mum River, two scenarios were proposed: the TUM plant was not considered in scenario S1, but was considered in scenario S2. The model results for scenario S2 indicated that the habitat was suitable for fish species living in the Mum River, with fish population numbers between 4.6 × 103 and 6.6 × 103. The S2 results indicated that the impacts of the TUM plant were negligible when compared with S1. Although the impact of the TUM plant on the Mum River is relatively large when the discharge is high (19 m3/s), calculations based on stable flow shows that the TUM plant could function well on the river ecosystem when the discharge is low or at normal rates. Therefore, this study shows that the TUM plant would be a good option to meet the needs of energy generation whilst having a minimal impact on river habitats and changes in fish species population in similar small rivers and streams.

Assessing the river habitat suitability and effects of introduction of exotic fish species based on anecohydraulic model system

An ecohydraulic model system was used to determine the levels of native fish species habitat suitability and assess the effects of two non-native fish species introduction in the Xiaonam River. The model system was developed by combining four models which are hydrodynamic, sediment transport, habitat and population models. The Light Belly fish (Schizothorax lissolabiatus) was selected as the native fish species. The Thorn Barb (Barbodes caldwelli) and Ray-finned fish (Acrossocheilus yunnanensis) were selected as non-native species. Water depth, flow velocity, substrates, and shear stress were used as suitability indicators for habitat and population models. A typical annual flow pattern was used to represent the discharge into the Xiaonam River. Numerical model simulations were created to determine native and non-native fish species' habitat suitability level and population density. The simulated results indicated that given atypical flow pattern, the habitat quality for native fish species was good and the population would remain table. The research showed that the habitat level in Xiaonam River was very suitable for Ray-finned fish but not for Thorn Barb. It also suggested that the Ray-finned fish was a suitable fish species to import into Xiaonam River and its population could increase steadily after introduction. The analysis indicated that the model developed and used in this study could yield valuable information on river ecological processes and fish monitoring programs.