Current Drainage System Research Articles

A Novel GIS-SWMM-ABM Approach for Flood Risk Assessment in Data-Scarce Urban Drainage Systems

Urbanization and climate change pose a critical challenge to stormwater management, particularly in rapidly developing cities. These cities experience increasingly impervious surfaces and more intense rainfall events. This study investigates the effectiveness of the existing drainage system in Lahore, Pakistan, a megacity challenged by rapid urbanization and the impacts of climate change. To address the lack of predefined storm patterns and limited historical rainfall records, we employed a well-established yet adaptable methodology. This methodology utilizes the log-Pearson type III (LPT-III) distribution and alternating block method (ABM) to create design hyetographs for various return periods. This study applied the stormwater management model (SWMM) to a representative community of 2.71 km2 to assess its drainage system capacity. Additionally, geographic information systems (GISs) were used for spatial analysis of flood risk mapping to identify flood-prone zones. The results indicate that the current drainage system, designed for a 2-year return period, is inadequate. For example, a 2-year storm produced a total flood volume of 0.07 million gallons, inundating approximately 60% of the study area. This study identified flood risk zones and highlighted the limitations of the system in handling future, more intense rainfall events. This study emphasizes the urgent need for infrastructure improvements to handle increased runoff volumes such as the integration of low-impact development practices. These nature-based solutions enhance infiltration, reduce runoff, and improve water quality, offering a sustainable approach to mitigating flood risks. Importantly, this study demonstrates that integrating LPT-III and ABM provides a robust and adaptable methodology for flood risk assessment. This approach is particularly effective in developing countries where data scarcity and diverse rainfall patterns may hinder traditional storm modeling techniques. Our findings reveal that the current drainage system is overwhelmed, with a 2-year storm exceeding its capacity resulting in extensive flooding, affecting over half of the area. The application of LPT-III and ABM improved the flood risk assessment by enabling the creation of more realistic design hyetographs for data-scarce regions, leading to more accurate identification of flood-prone areas.

Study of the Operating Cost of the Electric Pump for Mine Dewatering: Case of the SOMAÏR Uranium Mine

This study focuses on the operating cost of the electric pump used to extract water from the Artois mine owned by Société des Mines de l'AÏR. Exploitation of the SOMAÏR Artois mine uranium deposit is to be increased from the 20 m level to the 80, 100 or 120 m level; in the current phase of certain pits, access to the uranium deposit can only be achieved by a means that can draw off the water encountered. It is therefore essential to set up a drainage system to manage and evacuate the various water inflows. The main source of incoming water is the nearby water table, which is drained directly onto the mining unit. The current drainage system has two sumps capable of storing the various water inflows without incident. The energy balance for the three (3) years of pumping was drawn up using the electricity consumption data received. Peaks appear in August for the year 2021, followed by January 2020 and May 2022. The results show that specific energy is high, resulting in higher power consumption than water production. According to the graph of performance curves P = f(Q), the power ratings obtained for flows corresponding to the 24 m head are 25 kW at a flow rate Q = 49 l/s for pump 261; 35 kW, at a flow rate Q = 59 l/s for pump 259 and 35 kW at a flow rate Q = 105 l/s for pump 234.

Simulation Analysis of Urban Drainage System Utilizing StormDesk Software

Employing the data from comprehensive drainage system surveys and pipeline defect diagnostics, the StormDesk software was utilized to construct a SWMM model. This model facilitates the simulation of operational scenarios within the pipe network, both with the existing network defects and following their rectification, and provides crucial insight for the repair and renovation of the drainage infrastructure. The results indicate that the current drainage system in the study area is inadequate, with a high incidence of pipeline defects. This poses a significant flood risk during intense rainfall events. Given the projected increase in rainfall intensity, it is imperative to substantially enhance the drainage capacity of the existing system.

A Comprehensive Review of Drain Water Pollution Potential and Environmental Control Strategies in Khulna, Bangladesh

The main issues with drain water in Khulna, Bangladesh, include contamination, a lack of infrastructure, and sensitivity to seasonal changes. This review paper discusses the different causes of drain water pollution, such as inadequate drainage systems and poor waste disposal procedures, as well as the effects of this pollution on the environment, such as waterlogging and ecosystem contamination. The length of the current drainage systems in Khulna is roughly 528.120 km, with primary drains covering 175.43 km (33.22%), secondary drains spanning 150.45 km (28.49%), and tertiary drains spanning 202.24 km (38.29%). 291.230 km (55.14%) of these are pucca, or well-constructed drains, 51.790 km (9.81%) are semi-pucca, and 185.10 km (35.05%) are kutcha, or earthen drains. However, research on drainage density in 31 wards revealed that wards 23 and 31 had the highest and lowest drainage densities, respectively, of 33.88 km/km2 and 3.06 km/km2, with a citywide average of 11.79 km/km2. 51 primary outflow sites make up the drainage system in Khulna City, which is drained by the Bhairab, Rupsha, Mayur, and Gallamari rivers. Additionally, according to recent research by the Khulna Development Authority (KDA), just 33% of city residents have access to some type of drainage facility close to their homes, leaving roughly 67% without designed drainage systems. The drainage systems at KCC have been discovered to need further upkeep and cleaning. This paper intends to offer useful insights for policymakers, researchers, and environmentalists working toward a sustainable and healthy urban environment in Khulna by illuminating the amount of drain water pollution and outlining numerous alternatives.

Resilient Maintenance System to Avoid System Disruptions Due to External Shock: Application to Drainage System in Qatar

Many negative occurrences in any system cannot be linked to a single failure cause or system malfunction. They usually occur as a result of unforeseen combinations of typical performance variability. Disasters that human civilization has had to deal with in the past have highlighted the need of being ready and having the ability to quickly recover from a sudden and unexpected change in technological, organizational, social, and economic status of the community. Continuous emergences of business continuity disruptions lead to the global orientation towards resilience management application replacing the conventional risk assessment. The research studies risk assessment data prior to and after the emergence of resilience affecting shocks, and conducts a set of questions that will formulate resilience evaluation. The study proposed an evaluation framework of the current drainage system that will subsequently institutes a framework for a resilient system complimenting the main resilience attributes into three main models, and continuously improve its vulnerability status. The originality of this study lies on the unique demographical, geographical status of Qatar, the relative newness of drainage authority in Qatar and recent formation of its risk team.

Quantifying and improving flood resilience of urban drainage systems based on socio-ecological criteria

In this paper, a new framework is developed for evaluating the resilience of urban drainage systems (UDSs) under floods by proposing and quantifying some technical and socio-ecological (SE) criteria. The proposed criteria are used to quantify the seven principles of building resilience in socio-ecological systems. The criteria mainly focus on preserving diversity and multiplicity in a UDS, managing variables that gradually change over time (slow variables), improving structural and functional connectivity, maintaining system adaptability, encouraging learning, broadening participation, and promoting polycentric governance systems. For evaluating the efficiency of the proposed framework, it is applied to a real-world case study of improving resilience of the UDS in the eastern part of Tehran metropolitan area. Three scenarios for flood management are proposed based on the Low Impact Development (LID) practices which are simulated using the Storm Water Management Model (SWMM). The Entropy method is used to consider the uncertainty in the relative importance of different criteria in estimating the flood resilience. The estimated values for the proposed criteria regarding the current drainage system in the study area show its undesirable condition in many sub-catchments. The results also show that using around 2.3 km2 of LID practices in this urban watershed can significantly improve the resilience in many sub-catchments (nearly, 30%) and reduce the total volume of the overflow (about 50%). The results also show that using the flood management scenarios, improving connectivity is the most influential factor that enhances the general resilience of the system.

Evaluation on Merauke Drainage System in Overcoming Flood-Prone Areas

Merauke city suffers flooding in almost every rainy season, which endangers the environment and disturbs<br />people's activities. One of the worst floods happened in 2019, where flooding damaged vegetables and crops, impacted<br />the city's economy, and later caused economic inflation. Therefore, a study evaluating the drainage system in Merauke<br />city is needed to overcome this issue. This study was conducted through a field survey and literature study with data<br />that varies from hydrological, elevation, and hydraulics data. Hydrological data includes yearly rainfall data, and<br />hydraulics data consists of the drainage network and designs. This evaluation will then result in the normalization of a<br />drainage system. This study found that the capacity of the current drainage system is 10.815 m3/s, where this drainage<br />capacity cannot accommodate the amount of flood discharge plan. Also, the existing drainage system is missing a<br />component that was not built in the first place, affecting the drainage's capacity. Therefore, a normalization of the<br />drainage system is needed to avoid flooding.

Entrenchment of the Yellow River since the late Miocene under changing tectonics and climate

The distinctive right-angled bend of the Yellow River around the Ordos Block, a large Permo-Mesozoic continental block in East Asia, has attracted much attention from geomorphologists and geologists concerning its formation and evolution for more than a century. The Jinshaan Gorge, an over 600 km long entrenched reach of the Yellow River, currently connecting the Hetao Graben to the north and the Weihe Graben to the south, is considered to have developed in very recent geological time. However, the timing and processes of drainage integration between the two grabens and formation of the Jinshaan Gorge as a deeply incised form are still under debate, owing to limited data and various interpretations of them. In order to better understand the geomorphological evolution of the Yellow River, we investigated the sedimentology, magnetostratigraphy, and detrital zircon U-Pb dating in the upper Neogene and Quaternary deposits along the Jinshaan Gorge. We further integrated the new data with the sedimentary record of the adjacent basins in the northeastern Tibetan Plateau (NTP) and the basins around the Ordos Block, as well as the incision history of the Yellow River inferred from its terrace sequence. We show that the upper Neogene alluvial sediments preserved in the broad Tangxian valley along the Jinshaan Gorge are a mixture of materials from the Lvliang Shan and the Ordos Block. Importantly, they share almost the same provenance and zircon age spectra with the Pleistocene and Holocene Yellow River deposits. The broad Tangxian valley commenced incision during the Late Pliocene, followed by the formation of two Early Pleistocene terraces dated to ~2.2 Ma and ~1.2 Ma. The incision of the Yellow River and the accumulation in the basins were characterized by steady and slow rates before the Late Pleistocene, but an acceleration thereafter.We propose a three-stage evolutionary model for the development of the Yellow River, controlled by changing tectonics and climate during the Neogene. Before the late Miocene, an endorheic river system was developing in the Longzhong Basin. From the late Miocene to Early Pliocene, the Yellow River developed the current drainage system from the Longzhong Basin to the lower reach, constrained by the topographic pattern of the Ordos Block and its periphery, in turn controlled by coeval tectonic movements. Since the Late Pliocene, the Yellow River has undergone rapid incision with integration of the upper reach in the NTP and entrenchment in the upper and middle reaches, which were controlled by the continuously rising NTP and a deteriorating climate. The Tangxian valley developed and was filled between the end of the Miocene and Pliocene, approximately 8 to 3 Ma, and it was abandoned in the Late Pliocene in response to important climatic variations. The next acceleration in both incision and subsidence around the Ordos Block in the Late Pleistocene was also coeval with strong climatic oscillations, suggesting a possible link between climate and tectonics in the Neogene entrenchment history of the Yellow River.

Effect of Changing the Shape and Size of Inlet Area of Grates on the Hydraulic Efficiency of Urban Rainstorm Drainage Systems

Urban rainstorm drainage systems are used to collect the surface runoff from streets and other land surfaces through grate or curb openings that convey it to the drains. The quantity of surface runoff that is not discharged to the urban rainstorm drainage systems due to inadequate grate size or because the grate capacity is exceeded can cause flooding, immoderate hazards to drivers and pedestrians, and disrupt urban activities. This study aims to carry out experimental work to investigate the hydraulic efficiency of urban rainstorm drainage systems using different types of grates (shape and size of inlet area) for harvesting excess rainwater. Different grate shapes (five) with different inlet areas were investigated, as well as using three relative grate inlet areas (26%, 51%, and 64%). The results of the experimental work indicated that the best grate shape is the grate type 4 which provided the smallest reduction in discharge efficiency within 8.7%. The results specified that changing the size of the inlet area of grates from (26%) to (64%) has a significant impact on urban rainstorm drainage systems efficiency which decreased by 4%. In addition, the dimensional analysis principle with multi regression analysis were used to develop an empirical equation to compute the efficiency of urban rainstorm drainage systems. The relation between grate shapes and the relative inlet area with the efficiency of grate capture provides an indication to the decisionmakers to increase the time period for maintenance which will save the cost for further maintenance. The presented empirical equation can help decisionmakers for monitoring the current situation of grate blockage (relative grate inlet areas) and the corresponding efficiency. This study is beneficial for future road drainage system construction to avoid problems by assessing the performances of the current drainage systems and proposing mitigation measures to avoid improper functioning. Finally, this methodology can help to improve the efficiency of urban rainstorm drainage systems that can reduce the risks of urban floods.

Numerical study on water draining process pushed by nitrogen in EAST upper divertor

In the Experimental Advanced Superconducting Tokamak (EAST), the water in the cooling channels of the upper divertor is difficult to be pushed out by the current drainage system resulting in the possible divertor damage. Therefore, studies on the draining process using the gas pushing for this divertor is essential to improve the current drainage system. In this paper, the hydraulic characteristics of the developing gas-liquid two-phase flow were investigated in detail by using the FLUENT code. The results showed that the pressure difference between the inlet and outlet of the cooling channel should be larger than 4 kPa to effectively blow out the residual water from the cooling channels by the nitrogen gas pressure. Also, it was found that the draining process can be divided into five stages in regards to the different hydraulic characteristics, such as the flow velocity, the draining water flow rate, and the pressure distribution. These results will provide a theoretical basis for future improvements in the EAST drainage systems.

Hydraulic Modelling Analysis for Road Stormwater Drainage Evaluation under RCPs‎ Based Rainfall Data

Road drainage systems are often-constructed utilised design approaches not incorporating process-based depictions of possible hydrological responses, resulting in insufficient systems due to infrastructural development and climate change and ultimately, increased hydrological reaction. This study assessed possible effects of precipitation intensity variation following future severe rainfall events on the current road drainage system as whether pre-climatic stormwater drainage system could withstand potentially higher discharges and the need for modified design guidelines incorporating possible precipitation intensity variations due to ‎climate change. A case study was undertaken utilising rainfall data to develop an intensity-duration-frequency (IDF) curve representing precipitation volume variations due to climate change. The peak discharge and water level were simulated using hydraulic software program SWMM 5.1 for the existing open drainage system, wherein three future potential climate scenarios, namely 2030, 2040, and 2050 were simulated based on the RCP4.5 and RCP8.5 scenarios. The simulation results showed a tremendous future precipitation increment for RCP4.5 and RCP8.5 scenarios, yielding the following values, respectively: 28.8%, ‎‎43.7% and 34.6% and 65%, 61.5% and 75.5%. Therefore, the study findings and approach implemented should be considered when detailing assessments and preserving areas are at risk of high water flows. The study concludes that the existing road drainage system's inadequacy to manage copious rainfall amounts ‎anticipated due to climate change. Therefore, the study contributes to suggest the need for developing ‎drainage system magnitude using higher return periods to mitigate flood levels ‎on urban road networks.

Implementation of the hydraulic modelling of urban drainage in the northeast sector, Tunja, Boyacá

Historically, in the city of Tunja there has been a phenomenon of occupation of the natural channels of rainwater, altering the hydrology of the natural basins. Currently, the city is experiencing considerable and accelerated urban development towards the Northeast, which has resulted in overflows in the drainage system and floods that have affected residents. The current drainage system is not capable of registering the flow of water that leaves the urban sector due to a lack of instrumentation. In this study, precipitation and water flow equipment was installed in the northeastern district of the city, also known as Barrio Santa Ines. The basin was separated into 56 different sub-basins with physical and drainage parameters calculated for each sub-basin. The associated parameters were calibrated to the initial hydrological losses and roughness. A validated and calibrated urban drainage model was created in the program SWMM 5.1, allowing for the temporal hydrodynamic modelling of the system to be obtained. The model reproduces the real evolution of the system and was used in order to make predictions according to a maximum precipitation design event. This model resulted in the detection of two areas that are vulnerable to flooding. The identification of different sub-basins and the desegregation of the hydrodynamic model resulted in a reduction in the uncertainty of the evolution of water flow in the system.

Análise de eventos de inundação na sub-bacia do córrego Carneirinhos, João Monlevade, Minas Gerais

Desde a década de 1940 o número de pessoas que vivem nas cidades brasileiras dobrou, sendo que na maior parte delas o processo de crescimento ocorreu de modo desordenado, resultando em problemas socioambientais, inclusive inundações e deslizamentos de encostas nos períodos chuvosos. João Monlevade é um município mineiro que apresenta um histórico de desastres decorrentes de eventos hidrológicos extremos, assim, este estudo objetiva analisar os eventos de inundação registrados na sub-bacia do córrego Carneirinhos, seus respectivos impactos, bem como os sistemas meteorológicos atuantes no período de ocorrência. Primeiramente foi realizada a delimitação e caracterização da área de estudo, procedeu-se a coleta dos dados relacionados à série histórica dos eventos de inundações ocorridos na sub-bacia entre os anos de 1969 a 2020. Em seguida, identificaram-se os sistemas meteorológicos atuantes nas datas dos eventos. Pode-se constatar que o córrego Carneirinhos registrou 14 eventos de inundação que estão associados, principalmente, com a Zona de Convergência do Atlântico Sul ou com Zonas de Convergência de Umidade. Alguns possíveis fatores que podem justificar a ocorrência destes eventos são as alterações nos padrões hidrológicos devido às mudanças climáticas, a canalização do córrego, possíveis falhas no dimensionamento do projeto do sistema de drenagem da bacia, e/ou a combinação de todos estes fatores. Por fim, recomenda-se que sejam realizados estudos que avaliem o sistema de drenagem atual do município abordando o dimensionamento das galerias existentes frente às mudanças climáticas futuras, uma vez que alguns estudos apontam para um aumento na frequência dos eventos de inundação.

Hydrological and Hydraulic Analyses of Urban Storm Water Drainage System of Major Area of Pokhara, Nepal

The immense increase of the structural activity which decreases the pervious area of the city is alarming danger situation pertaining to drainage. Urbanization and improved area of imperviousness are the major contributors that make the existing drainage network insufficient while inadequate maintenance and haphazardly throwing rubbish on the road and drain are other issues. The major objective of the study is to analyze the hydrological and hydraulic status of the urban storm water drainage system of the major area of Pokhara City of Nepal and to compare the calculated result with existing situation, using Rehm tools HYKAS and GraPS under AutoCAD environment. The results of this study show that the size of the existing road side drains is inadequate to handle all the surface runoff. It is found that the existing situation of the drainage system is quite poor and need to be redesign or reconstruct immediately. The hydraulic load of almost all the conduit is beyond the limit assigned. The hydraulic design of the most of the drainage conduit is inadequate and re-design of the drain is essential based upon accurate flow estimation methods. This study concludes that the applicability of the current drainage system is quite poor and needs to make certain changes with their construction immediately in order to avoid any danger and adverse effect possessed by surface flooding over the road surface and other paved surfaces. The surface runoff is significantly increased compared to the situation before the construction of existing drainage system and therefore for the appropriate storm water management of the urban area of Nepal, it is critical to design the drainage system based on both hydrological and hydraulic analyses considering reliable data.

40 Ar/ 39 Ar mica dating of late Cenozoic sediments in SE Tibet: implications for sediment recycling and drainage evolution

The Indo-Asia collision significantly changed the topography and drainage network of rivers around the Tibetan Plateau. Debate continues as to when and how the current drainage system of the Yangtze River was formed. Here we use 40 Ar/ 39 Ar dating of detrital micas (muscovite and biotite) to constrain provenances of the Pliocene sediments from the Jianchuan and Yuanmou basins in SE Tibet. Muscovite and biotite data of the same Pliocene samples from the Jianchuan Basin suggest contrasting distal v. local sources, respectively. Similarly, muscovite data of the Yuanmou Basin suggest a derivation of sediments from the Yalong River, but the characteristics of the Pliocene cobbles (palaeocurrent and subrounded cobbles) suggest that these sediments are locally sourced. Sediment reworking is proposed as an explanation for the different sediment provenance signals in the Jianchuan and Yuanmou basins that have led to the controversy of an either Pleistocene or pre-Miocene age of formation of the current Yangtze. Based on sediment provenance constraints, the evolution of the Jinsha River is reconstructed. The upper Jinsha River lost its connection with the southward flowing Red River upstream from the Jianchuan basin at least before the Pliocene. At the same time a parallel site in the Yuanmou Basin shows that the Yalong River stopped flowing southward into this basin. Detrital mica from early Pleistocene sediments at the Panzhihua site between the Jianchuan and Yuanmou basins is sourced from the current Jinsha and Yalong rivers. These results would suggest that the current upper Yangtze drainage system should have been established before the Pliocene. Supplementary material: Muscovite 40 Ar/ 39 Ar data, biotite 40 Ar/ 39 Ar data and muscovite geochemistry are available at https://doi.org/10.6084/m9.figshare.c.4821573

A nonstructural flood prevention measure for mitigating urban inundation impacts along with river flooding effects

In recent decades, urban developments along rivers have experienced high flooding risks, elevated by increasing urbanization. Due to the expansion of urban areas, flood mitigation strategies must rely on nonstructural flood management policies. This study evaluated the impacts of pluvial floods considering fluvial flooding effects through field surveys and numerical model simulations. Nonstructural flood protection measures are provided by establishing warning water levels based on variant scenario simulations. The results reveal that the aggravated drainage system overflow induced by elevated river water is significant when considering river flooding effects. As a result, current drainage systems have failed to meet the designed flood protection standards, indicating the need to produce potential inundation maps and to establish warning water levels. To prevent the main evacuation route of each settlement from being blocked due to flooding, the proposed warning water levels support timely and effective evacuations. Public community centers and schools in noninundation areas near settlements were identified as possible shelters based on the proposed warning water levels and inundation maps. We conclude that although the riverside areas without dike protection could sustain natural environments and landscapes, they must incorporate nonstructural flood protection measures. At the same time, it must be considered that river flood levels may reduce urban drainage capacity.

Perceptions on Floods by the Population Residing in the Watershed of Ribeirão Garcia, Brazil

Any anthropic action transforms the environment. However, the Urbanization is a human achievement, not the “villain” or “protagonist” of passive actors and experienced environmental degradations, but the model of urban occupation, construction and densification, interconnected with the ineffectiveness of the current drainage system. When evaluating programs to minimize flood impacts, the social component is a necessary but often neglected dimension. This component can be evaluated through the articulation between the actors (population and public power) and the resident community’s perception in relation to the needs and interventions. The present work seeks to analyze the perception of the community resident in the watershed of Ribeir&#227o Garcia regarding the problems arising from urban floods. The repeated flood events occurring in the Ribeirao Garcia watershed in the city of Blumenau-SC, Brazil, make this place a potential area for an investigative process, which can subsidize future decision-making processes aimed at the adequacy of a sustainable system in medium and long term. For the accomplishment of this work, a qualitative research was adopted. Fieldwork and semi-structured interviews with residents in the sample areas have been carried out to analyse land use and occupation. The procedures that supported this sample survey were divided into four steps: definition of the total population and the sample size; preparation of a questionnaire; application of the questionnaire and tabulation of results. It can be seen that, despite the problems of floods and landslides to residents of all sample areas, the locals have different perceptions regarding the proposed issues and that these different perceptions are linked to the sample geographic location. The analysed space is full of contrasts in physical, social and economic aspects, which favours one part of the population and disfavours the other. The process of densification and overcrowding of inadequate areas has been one of the negative effects of a disorganized housing sector in a speculative real estate market, and different levels of infrastructure among the districts, consolidating, in many ways, a process of social exclusion and spatial segregation. The analysis of the resident community’s perception in the Ribeirao Garcia watershed shows that the most susceptible communities to this type of events are those of low income, located in risk areas. It also demonstrates that, despite these communities’ present empirical situation knowledge on the causes and consequences of the floods, most residents prefer to transfer responsibility only to the public power, without assuming their own responsibility. The study of community perception makes it clear that the problem has been aggravated in part by a lack of knowledge of the relationship between land use and flooding.

Augmenting Drainage System in the Old Town of Kuching, Sarawak, Malaysia

Padungan, one of the busiest business districts within Kuching City has been facing difficulties due to its age and inability to manage urban runoff. To sustain its historical heritage value without compromising the beauty and ability to discharge urban runoff, environmental needs have called for a change in urban stormwater management. The main objective of this study is to incorporate StormPav Green Pavement along the backstreet of Padungan and to investigate the effectiveness of the permeable road. The methodology used in this study is by means of computer modelling using Storm Water Management Model (SWMM). There are two models built, simulating conditions as (a) current drainage system facility; (b) implementing StormPav Green Pavement along the back of Padungan Street for the purpose of accommodating runoff from the whole two rows of buildings. From the analysis of modelling scenes, implementing the permeable road is a preferable solution as it encompasses both the present and future needs into the design consideration.

Population Genetic Structure of Cnesterodon decemmaculatus (Poeciliidae): A Freshwater Look at the Pampa Biome in Southern South America.

The Pampas is a Neotropical biome formed primarily by low altitude grasslands and encompasses the southernmost portion of Brazil, Uruguay, and part of Argentina. Despite the high level of endemism, and its significant environmental heterogeneity, Pampean species are underrepresented in phylogeographic studies, especially aquatic organisms. The Pampean hydrological system resulted from a long history of tectonism, climate, and sea level changes since the Neogene. In this study, we examined the population genetic structure of Cnesterodon decemmaculatus, a freshwater fish species that occurs throughout most of the Pampa biome. We characterized mitochondrial and autosomal genetic lineages in populations sampled from Southern Brazil and Uruguay to investigate (1) the correspondence between current drainage systems and evolutionary lineages, (2) the demographic history for each genetic lineage, and (3) the temporal depth of these lineages. Overall, we found that the major evolutionary lineages in this species are strongly related to the main Pampean drainage systems, even though stream capture events may have affected the distribution of genetic lineages among drainages. There was evidence for recent population growth in the lineages occupying drainages closest to the shore, which may indicate the effect of quaternary sea-level changes. In general, divergence time estimates among evolutionary lineages were shallow, ranging from 20,000 to 800,000 years before present, indicating a geologically recent history for this group, as previously reported in other Pampean species. A Bayesian phylogeographical reconstruction suggested that an ancestral lineage probably colonized the Uruguay River Basin, and then expanded throughout the Pampas. This evolutionary scenario may represent useful starting models for other freshwater species having a similar distribution.

Hydrosalinity balance and critical ratio of drainage to irrigation (RDI) for salt balance in Weigan River irrigation district of the Tarim basin (China)

The analysis of the principle of salt mass balance in irrigation districts is the foundation for the rational drainage system design and its effective evaluation. The salt balance of the Weigan River irrigation district is analyzed using annual measured data. Factors affecting the ratio of drainage to irrigation (RDI) and methods for determining this ratio are discussed. The results show that RDI is related to the volume and salt content of irrigation water and drainage water. The critical RDI for the Weigan River irrigation district is 9.29%. It is necessary to achieve a certain level of percolation to maintain the hydrosalinity balance when planning irrigation schedules and managing irrigation and drainage. Moreover, urgent improvement of the current drainage system is required to ensure that the actual RDI is greater than the critical RDI in the irrigation district. From 1994, the irrigation district turned from salt accumulation to desalinization, and the ratio of drainage to irrigation tended to optimal value.