Habitat suitability modeling of a conservation-significant fish species of the Kosi River,Uttarakhand, India

Water quality plays a vital role in the sustenance of aquatic life, including fish. Therefore, an inclusive understanding of water quality parameters can be considered an essential step in framing the conservation and management strategy of an aquatic ecosystem. This study examines the habitat suitability of a conservation-significant fish, the Tor putitora, and two associated fishes, the Labeo dyocheilus and the Garra gotyla, in relation to the water quality parameters of the Kosi River. Four crucial water quality parameters, water temperature, dissolved oxygen, electrical conductivity, and pH, were included in the QUAL2K modeling. Furthermore, hydrological processes were modeled using the soil and water assessment tool, and flow was used as an input in the QUAL2K model. The simulated water quality was correlated with fish habitat and analyzed through the analytical hierarchical process (AHP). Results suggested that the habitats of the Kosi were more suitable in the post-monsoon rather than pre-monsoon. Tor putitora, the flagship species of the Kosi, preferred the river habitats with a lower water temperature and higher dissolved oxygen for spawning. Thus, we recommend securing such habitats and managing them in collaboration with local communities for the long-term conservation of this endangered Himalayan species.     

淮北采煤塌陷区两个小型湖泊轮虫的群落结构特征

于2017年4月、7月、10月和2018年1月对淮北采煤塌陷区东湖和刘桥湖两个小型湖泊进行采样调查,探讨轮虫群落结构的季节变化及其与环境因子的关系。东湖共记录轮虫13科15属32种,刘桥湖共记录10科12属25种。东湖轮虫的年平均密度和生物量(2 722个/L和3.04 mg/L)明显高于刘桥湖(1 311个/L和1.30 mg/L);东湖主要优势种为刺盖异尾轮虫、暗小异尾轮虫、长肢多肢轮虫、长三肢轮虫、广布多肢轮虫和螺形龟甲轮虫,刘桥湖主要优势种为暗小异尾轮虫、长肢多肢轮虫、小链巨头轮虫、广布多肢轮虫、螺形龟甲轮虫和迈氏三肢轮虫;东湖和刘桥湖水体呈中度富营养状态;水温、总氮、总磷和叶绿素a质量浓度是影响两湖轮虫群落结构变化的重要因素,鲢、鳙鱼的捕食压力间接影响了两湖轮虫群落结构的变化。     

Aspects of the biology of Labeo cylindricus (Pisces: cyprinidae) in Lake Baringo,Kenya

Aspects of the biology of Labeo cylindricus from Lake Baringo were investigated, based on experimental beach seining and gillnetting between August and October 2007. The length–weight relationship indicated the species exhibited positive allometric growth (b = 3.7083), with a condition factor (K) of 0.84 ± 0.0298 S.D. Males dominated fish catches, with an adult sex ratio of males/females of 1:1.7. The fish length‐at‐50% maturity (Lm50) was 127.7 and 126.1 mm total length (TL) for males and females, respectively. Fish age and growth were determined from sagittal otoliths considered to be from the young‐of‐the‐year. Clear circuli observed in the otoliths were used to determine fish age in days. Validation by oxytetracycline marking indicated that a single growth increment (1.1 ± 0.1 SE) is formed daily on fish otoliths. Fish length (TL mm) was correlated significantly with age (in days), TL = 1.398 Age + 26.523 (r² = 0.91). Fish growth was subsequently estimated to be 1.398 mm day^?1. The weights and ages (in days) of fish exhibited a significant (P < 0.05) power relationship defined by the equation: W = 0.0003 Age^2.5804 (r² = 0.88). The results of this study provide parameters that, if appropriately monitored, can be used to predict responses of fish populations in Lake Baringo and elsewhere to human interventions (exploitation) and natural environmental change.     

Effect of regulation on 0+ fish recruitment in the great ouse,a lowland river

The recruitment of 0+ fishes in the River Great Ouse, East Anglia (U.K.), was investigated using electrofishing by Point Abundance Sampling, in order to compare the distribution and extent of fish reproduction in the river and its annexes (side channels, backwaters, etc.) with similar but unregulated lowland rivers of Europe. In all, 44 sites were sampled during three weeks in August 1989. Correspondence Analysis of the Sites-by-Species matrix (44 × 17) in density (fishes per m²) revealed a slight but notable longitudinal zonation of fish reproduction, unusual for lowland rivers, with the limnophils Blicca bjoerkna (L.), Scardinus erythrophthalmus (L.) and Abramis brama (L.) limited to lentic downstream sites and the rheophil Barbus barbus (L.) restricted to a few upstream sites. Thus, compared with unregulated rivers of Europe, the River Great Ouse differs by: (1) the absence of pelagic spawners, e.g. Lota lota (L.), which were historically reported as abundant; (2) the reduced range and abundance of both rheophilic and limnophilic cyprinids, e.g. B. barbus (L.), Alburnus alburnus (L.) and Blicca bjoerkna (L.), Scardinus erythrophthalmus (L.), Abramis brama (L.), Tinca tinca (L.); and (3) the predominance of generalists throughout the system, Rutilus rutilus (L.) downstream and Phoxinus phoxinus (L.) with Gasterosteus aculeatus (L.) upstream, probably to the additional detriment of the localized specialists, both limnophilic and rheophilic.     

Growth,mortality and recruitment of Nile perch (Lates niloticus) in Lake Victoria,Kenya

This study investigated the growth, mortality and recruitment of Lates niloticus in Lake Victoria basis on length–frequency data collected during the period 2014‐2015. The asymptotic length (L _∞ ) had a value of 124 cm TL , growth curvature (K ) of 0.22 year^?1, total mortality (Z ) of 0.96 year^?1, a natural mortality (M ) of 0.42 year^?1, a fishing mortality (F ) of 0.54 year^?1, an exploitation rate (E ) of 0.57 and a growth performance index () of 3.53. Logistic selection model showed that 50% of fish of 46.09 cm TL encountering the gear are retained. There were two peak recruitment periods, a minor one in March and a major one in July, accounting for 12.04% and 22.04%, respectively, of the total fish catch. The Beverton and Holt's relative yield‐per‐recruit model indicated the indices for sustainable yields are 0.32 for optimum sustainable yield (E _0.5), 0.60 for maximum sustainable yield (E _max) and 0.51 for economic yield (E _0.1). Compared to previous findings, there is a great decline in the sizes of Nile perch stocks in Lake Victoria. Thus, managing the fishery requires strict adherence to the slot size of 50–85 cm TL , and restrictions on illegal gear and methods, by the devolved governments through monitoring, control and surveillance in liaison with the Beach Management Units (BMU s).     

夏季朱衣河二氧化碳分压分布特征及影响因素分析

为研究夏季三峡水库支流库湾-朱衣河的水体二氧化碳分压(p(CO_2))分布特征及影响因素,于2016年7月进行两次分层采样。根据水体的碳酸平衡原理和亨利公式计算水体p(CO_2)并利用水体中超额的二氧化碳分压(E_(p(CO_2)))和表观耗氧量(AOU)的比值(E_(p(CO_2))/AOU)表征生物好氧呼吸作用对p(CO_2)影响程度,研究结果为:上游表层水体的p(CO_2)变化范围大概在5.14~53.67 Pa,受使水体中H+减小的浮游植物光合作用影响较大,导致碳酸盐平衡向右移动,水体中CO_2极不饱和;5 m以下分层水体的p(CO_2)随着水深有变大的趋势,变化范围最低是26.04 Pa,最高是117.28 Pa,而?E_(p(CO_2))/?AOU值高达1.04~2.91,远高于评估上限值,其主要受外源碳汇入影响明显;河口的p(CO_2)大概为39.93 Pa,?E_(p(CO_2))/?AOU的值为0.64±0.01,受生物好氧呼吸作用影响显著;整体的p(CO_2)与温度(T)、pH、溶解氧(DO)、叶绿素ɑ(Chl-a)、硝氮(NO_3~-)存在显著的负相关关系,与浊度(TD)有显著的正相关性,与溶解有机碳(DOC)无显著相关性。     

Bi-site Analysis of Meteorological Drought Duration: Theoretical Modeling and Application

Droughts are regional incidents that threat the environment and limit most of the socio-economic activities. Given the dry and wet state sequences for two sites, X_t^{( 1 )}X_t^{\left( 1 \right)} and X_t^{( 2 )}X_t^{\left( 2 \right)} , this paper presents a procedure to reduce the two sequences X_t^{( 1 )}X_t^{\left( 1 \right)} and X_t^{( 2 )}X_t^{\left( 2 \right)} to one sequence Z _t for the purpose of simplifying the analysis of drought duration at two sites jointly. Theoretical models to evaluate the expected value and the variance of the process Z _t and the occurrence probability of the dry state at two sites jointly are presented and verified using simulation experiments. Historical data for the period 1939–2005 and generated rainy season precipitation data for two gauging sites in Central Jordan, namely Amman Airport and Madaba, is used in the present study to investigate the occurrence of droughts. The joint analysis of drought duration obtained using the historical precipitation at the two sites appears to be inconsistent especially for droughts of duration longer than 3 years. On the other hand, the joint analysis of drought duration obtained theoretically by employing the characteristics of the process Z _t are found to match well with the more reliable drought statistics obtained empirically by analyzing the long generated precipitation. Considering 25 years planning horizon, droughts of 1, 2, and 3 years duration are the most frequent droughts in the region of Central Jordan. The return period of such regional droughts ranges from 8–30 years.     

Wavelet Transform Method for Synthetic Generation of Daily Streamflow

Synthetic generation of daily streamflow sequences is one of the most critical issues in stochastic hydrology. In this study, a new wavelet transform method is developed for synthetic generation of daily streamflow sequences. Firstly, daily streamflow sequences with different frequency components are decomposed into the series of wavelet coefficients W ₁(t), W ₂(t),...,W _P (t) and scale coefficients (the residual) C _P (t) at a resolution level P using wavelet decomposition algorithm. Secondly, the series of W ₁(t), W ₂(t),...,W _P (t) and C _P (t) are divided into a number of sub-series based on a yearly period. Thirdly, random sampling is performed from sub-series of W ₁(t), W ₂(t),...,W _P (t) and C _P (t), respectively. Based on these sampled sub-series, a large number of synthetic daily streamflow sequences are obtained using wavelet reconstruction algorithm. The advantages of this newly developed method include: (1) it is a nonparametric approach; (2) it is able to avoid assumptions of probability distribution types (Normal or Pearson Type III) and of dependence structure (linear or nonlinear); (3) it is not sensitive to the original data length and suitable for any hydrological sequences; and (4) the generated sequences from this method could capture the dependence structure and statistical properties presented in the data. Finally, a case study in Jinsha River, China, indicates that the new method is valid and efficient in generating daily streamflow sequences based on historical data.     

Hydraulic effects of aquatic weeds in U.K. rivers

The effects of large aquatic plants (aquatic macrophytes) have been given limited attention in literature dealing with open channel flow. This is despite a large number of river channels in the U.K. being affected by profuse growths of these plants. This paper contributes to three major areas in relation to aquatic macrophytes and river channels. First, a literature review examines four areas of vegetated channel research. Early work on vegetated channels concentrated upon grass-lined farm drainage channels in the U.S.A. This was complemented by flume studies of predominantly artificial vegetative roughness elements. The review discusses research into large aquatic plants in stream channels, and the discussion draws together a number of disparate areas of research into vegetated channels including theoretical considerations. Secondly, the paper discusses results obtained from laboratory flume experiments, using real plants, and field monitoring on the River Ebble, Wiltshire, U.K. The relationship between discharge and Manning's roughness coefficient (n) is examined. Field monitoring results are presented as generalizations in the relationship between Manning's n when the monitoring sites were vegetated and unvegetated. The relationship between plant cover in the channel and Manning's n is also examined. Two measurements of plant cover are employed: the percentage cross-sectional area of channel vegetated, and biomass per unit area. The field data for Manning's n and discharge are then discussed in detail in a case study of one site on the River Ebble. Finally, the results obtained from field monitoring are compared to previous research. In the light of these comparisons and detailed examination of the field and flume data, a conceptual model of the effects of aquatic plant growth on channel roughness, mean flow depth, and flow stage is represented. Using this model, an estimate can be made of the likely effect of changing plant cover and discharge on flow stage in an open channel.     

Parametric Method of Fault Location in Distribution Networks

A method for determining the distance to a fault (l) is suggested for medium-voltage distribution networks. The method is based on allocating the upper natural frequency (f ₂) due to the discharge of the capacitance of the damaged phase in the transient process of earth connection. The allocated frequency and frequency response l = (f ₂) calculated for the damaged line are used to locate the fault.     

Approximate Methods for the Estimation of Muskingum Flood Routing Parameters

There are a variety of techniques for estimating the parameters x and K of the Muskingum method of flood routing. One common difficulty in all the approaches is that different storm sequences along the same river reach would typically yield different parameter estimates. The a statistical analysis of these parameters also shows that they are highly variable. As a result achieving of a high level accuracy may not be the principle issue in describing x and K. This paper presents two approximate methods for estimating these parameters rather easily. The first method requires the computation of the slopes of the inflow and outflow hydrographs at their point of intersection, and the computation of the maximum storage within the reach. The second method requires the computation of the inflow and outflow hydrographs at two specific points. Three case studies investigated show that the first method gives estimates for the Muskingum parameters comparable to those derived by traditional estimation procedures for hydrographs showing linear characteristics.     

Impact of Flood Spreading on Infiltration Rate and Soil Properties in an Arid Environment

Flood spreading (FS) is one of the suitable methods for flood management and water harvesting that increases the groundwater recharge, makes soil more fertile and increases nutrients in soil. It is also a method for reusing sediment, which is usually wasted. The purpose of this paper is to investigate the impact of flood spreading on physical and chemical soil properties (soil texture, infiltration rate, pH, EC, Na, P, K, Ca, Mg, Cl, HCO₃, and SO₄). It is examined that the soil properties change in the flood spreading projection area (FSP). The physico-chemical properties of soil and infiltration rate were measured in different soil depths at both flood spreading and control area. For the 20 cm of top soil, the amount of clay increased after the flood spreading implementation especially in the first and second dikes. Increasing clay was accompanied by decreasing soil infiltration and sand percentage. The mean differences of the clay, sand and infiltration rate between FSP and the control area were statistically significant (P < 0.01). A significant difference was not observed in 20–30 cm of the depth. Soil pH, Mg, HCO₃, Cl and SO₄ in different soil layers did not show any significant difference between the control and FSP. Soil EC in 0–20 cm depth of FSP and control area was showed a significant difference (P < 0.05) but no significant differences were found in deeper layers (P < 0.05). K, Na and Ca were remarkably different between 0 and 10 cm depths (P < 0.05) whereas no significant differences were found in deeper layers (P < 0.05). Comparison of the physico-chemical properties and infiltration rates between the dikes in the FSP shows that there are the significant differences between the medians of dike 1 with dikes 2, 3, 4 and 5, but the differences were not observed between dikes 3, 4 and 5. Our results show that the flood spreading operation can be influenced by the area that is under this operation. This study allowed us to investigate the mechanisms that regulate the infiltration rate and chemical soil properties throughout a seasonally flooded area.     

粗粒土孔隙比及级配参数与渗透系数概率的相关性研究

孔隙比和颗粒级配是粗粒土渗流力学特性的重要影响因素。利用Copula理论适合建立多个非独立变量间联合分布函数的优点,以渗透试验成果为数据基础,构造了反映粗粒土渗透系数k、孔隙比e、级配不均匀系数Cu和曲率系数Cc间相关关系的四维最优Archimedean Copula函数(即Nelsen No 13,四维单参数对称Archimedean Copula函数)。利用构造的最优四维Copula函数求条件概率,便可得到粗粒土渗透系数估值的保证率,或者计算在一定保证率条件下的渗透系数。通过比较渗透系数试验值与Copula函数法、Terzaghi法及Hazen法计算值,阐述了Copula理论用于粗粒土渗透参数估值的可靠性。     

Test of a Benthic Macroinvertebrate Habitat—Flow Time Series Model Incorporating Disturbance and Recovery Processes

We tested a model [Benthic Invertebrate Time series Habitat Simulation (BITHABSIM)] for simulating the effect of changes in flow on benthic macroinvertebrate habitat and relative abundance. The model calculates a habitat index (WUA2) based on weighted usable area (WUA) modified to account for reduction of invertebrate abundance by flood disturbance and drying followed by recolonization. The test involved a comparison of WUA and WUA2 with a 1‐year abundance time series of the common New Zealand mayfly Deleatidium spp. in a small gravel‐bed river with naturally variable flows. The fit of WUA and WUA2 to the Deleatidium spp. abundance time series was judged on correlation and regression analysis of the magnitudes and slopes of the mean‐standardized indices and abundance versus time. WUA fit the low flow part of the abundance time series fairly well, but not the portion after flood disturbance. Over the entire time series, WUA fit Deleatidium spp. abundance and rate of change poorly. WUA2 fit Deleatidium abundance better, but the correlation was not quite statistically significant at the 95% level. However, it did explain the essential temporal pattern. The fit of the slopes of standardized WUA2 to the slopes of standardized Deleatidium spp. abundance was significant (R² = 0.66), but with a systematic bias; high slopes were underestimated and low slopes overestimated. BITHABSIM adds biological realism to traditional hydraulic‐habitat modelling based on WUA and so improves the reliability of assessments of effects of flow change on benthic macroinvertebrates over the entire hydrograph. Parameter uncertainty and research needs to improve BITHABSIM and future process‐based models are discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Growth,mortality and recruitment of silver cyprinid (Rastrineobola argentea) in the open waters of Lake Victoria,Kenya

This study investigated the growth, mortality and recruitment of Rastrineobola argentea in Lake Victoria on the basis of length–frequency data collected during the period 2014–2015. The asymptotic length (L _∞ ) had a mean (±SE ) value of 53.50 ± 0.50 mm SL , growth curvature (K ) of 0.81 ± 0.06 year^?1, total mortality (Z ) of 2.96 ± 0.12 year^?1, a natural mortality (M ) of 1.23 ± 0.06 year^?1, a fishing mortality (F ) of 1.74 ± 0.07 year^?1, an exploitation rate (E ) of 0.59 ± 0.01, a growth performance index (?′ ) of 3.36 ± 0.02 and a length at 50% capture (L ₅₀) of 28.25 ± 0.43 mm SL . The fish exhibited a peak breeding during the months of May and August. The Beverton and Holt relative yield‐per‐recruit model indicated mean (±SE ) indices as 0.37 ± 0.01 for optimum sustainable yield (E _0.5), 0.76 ± 0.01 for maximum sustainable yield (E _max) and 0.66 ± 0.01 for economic yield (E _0.1). Compared with previous studies, there is a great decline in the sizes of R. argentea stocks in Lake Victoria. Thus, management measures should include restriction on illegal seine nets <10 mm mesh size and re‐enforcement of a fishing ban or a closed season.     

Development of Regional Rainfall Annual Maxima for Southwestern Iran by L-Moments

L-moment procedures are applied to develop regional rainfall annual maxima (maximum 24-h rainfall occurring annually), considering complex physiographic and hydroclimatological features and weather processes as attributes influencing regional homogeneity. Capability of L-moment procedures in breaking down large areas into coherent and homogeneous sub-regions is investigated. The study area of 238,630 km² is located in southwestern Iran, representing 154 rainfall recording gauges of rather complex orographic features. According to the results and considering the extreme value nature of the analysis, i.e., rainfall annual maxima, it was possible to establish four homogeneous sub-regions, representing areas of 80,490 km², 75,880 km², 31,810 km² and 50,450 km². The L-moment procedures successfully evaluated the homogeneity analyses and assignment of appropriate regional probability distribution functions (PDFs) to individual sub-regions. Flood potential maps and associated rainfall depth-area information were provided for individual sub-regions. The proposed heterogeneity measures by Hosking and Wallis (Water Resour Res 29(2):271–289, 1993), known as H ₁, H ₂ and H ₃ tests were further investigated in this research. The results of this research confirmed findings of Hosking and Wallis (Water Resour Res 29(2):271–289, 1993), i.e., strong capability of H ₁ as a heterogeneity measure, and lack of capability of H ₂ and H ₃ measures for distinguishing between homogenous and heterogeneous regions.     

Step‐drawdown tests

The analytical results of step‐drawdown test data from the study area in Bengal suggest that most test wells were not properly developed with adequate pumping prior to the test and that a significant amount of well development took place during the test exercise. The aquifer loss factor (B₁ ) ranges from a maximum of 19.3 sec/ft² for Nabinagar to a minimum of 7.0 sec/ft² for Chandina. The well loss factor (C₁ ) does not indicate any major abnormality and ranges from a maximum of 1.49 sec²/ft⁵ for Nabinagar to a minimum of 0.96 sec²/ft⁵ for Laksam and is supported by the minimal differences between the measured and the calculated drawdown values. Highly efficient well conditions are obtained for all the test wells. The unrealistic step‐drawdown test procedures and poor prior development of wells have considerable influence on the dissimilar transmissivity values calculated from step‐drawdown test data.