Annual Maximum Streamflow Research Articles

Variação temporal do comportamento hidrológico na bacia do Rio Dourados no período de 1973 a 2002

A bacia do Rio Dourados localiza-se na sub-bacia do Rio Ivinhema que, por sua vez, se insere na Bacia Hidrográfica do Rio Paraná. A região é de grande potencial para o desenvolvimento agrícola e, com o crescimento da agricultura irrigada, o conhecimento das características hidrológicas dessa bacia é de grande importância para que o aproveitamento de suas águas possa ser otimizado com menor impacto ambiental. Neste trabalho, procedeu-se à análise do comportamento hidrológico na Bacia do Rio Dourados, tomando-se, para tanto, dados observados na estação Porto Wilma, situada próxima à foz da bacia. Foram obtidas a precipitação média anual, a vazão média anual, a vazão máxima anual, a vazão mínima anual de sete dias de duração, a vazão associada à permanência de 95% e o coeficiente de deságüe. Os resultados encontrados permitiram constatar variações pouco significativas para as vazões média e máxima e a tendência de diminuição com o tempo da vazão mínima com sete dias de duração e do coeficiente de deságüe. Associados às altas significâncias dessas variáveis hidrológicas, os resultados mostram a nítida interferência nas condições de escoamento do Rio Dourados durante os meses com menor incidência de precipitação.

Possible influence of ENSO on annual maximum streamflow of the Yangtze River, China

Variability and possible teleconnections between annual maximum streamflow from the lower, the middle and the upper Yangtze River basin and El Nino/Southern Oscillation (ENSO) are detected by continuous wavelet transform (CWT), cross-wavelet and wavelet coherence methods. The results show that: (1) different phase relations are found between annual maximum streamflow of the Yangtze River and El Nino/Southern Oscillation (ENSO) in the lower, the middle and the upper Yangtze River basin. In-phase relations are detected between annual maximum streamflow of the lower Yangtze River and anti-phase relations are found in the upper Yangtze River. But ambiguous phase relations occur in the middle Yangtze River, showing that the middle Yangtze River basin is a transition zone. Different climatic systems control the upper and the lower Yangtze River. The upper Yangtze River is mainly influenced by the Indian summer monsoon and the lower Yangtze is mainly influenced by the East Asian summer monsoon; (2) as for the individual stations, different phase relations are found in the longer and the shorter periods, respectively. In the longer periods, the annual maximum streamflow is more influenced by climatic variabilities, while in the shorter periods, it is influenced by other factors, e.g. human activities. The results of the study provide valuable information for improving the long-term forecasting of the streamflow using its relationship with ENSO and the Indian Monsoon.

Artificial-intelligence-based detection tests for the identification of shifts and trends in Canadian hydrometric data

Two artificial-intelligence-based detection tests for the identification of shifts and trends in data sequences are described and applied to Canadian hydrometric data. These tests are based on the Kohonen neural network and fuzzy c-means approach. They are applied for the detection of shifts and trends in annual mean and daily maximum streamflow data from 43 Canadian hydrometric stations. The results of the tests are compared with those from conventional detection tests, such as the Mann–Whitney test for shifts and the Mann–Kendall test for trends. These results support conclusions from previous studies about the presence of trends in Canadian hydrometric data. As a whole, the artificial-intelligence-based and conventional tests may be used to confirm one another. In some cases, given their respective strengths and weaknesses, the tests may complement one another. One should therefore consider the use of more than one detection test for determining the presence or absence of anomalies in data sequences.Key words: hydrometric data, detection tests, shifts, trends, artificial intelligence.

Observed trends of annual maximum water level and streamflow during past 130 years in the Yangtze River basin, China

Annual maximum streamflow and annual maximum water level and their variations exert most serious influences on human society. In this paper, temporal trends and frequency changes at three major stations of Yangtze River, i.e. Yichang, Hankou and Datong representing upper, middle and lower reaches, respectively, were detected with the help of parametric t-test, Mann–Kendall (MK) analysis and wavelet transform methods. The results show that: (1) there is a significant upward trend in streamflow at middle Yangtze River, indicating that flood hazard in the middle reach of the river, the flood rich region, will be more serious; (2) there is a consistent increase of water level from upper to lower reaches of the river which does not always coincide with the maximum streamflow variations; and (3) the periods of water level changes are decreasing over time, indicating the increasing occurrence frequency of annual maximum water level over time. This phenomenon is more obvious from upper Yangtze River to the lower Yangtze River. Human activities like destruction of vegetation, land reclamation and construction of levees reduced lake sizes and filled up the river bed, reducing the flood storage capacity of lakes and fluvial channel. These factors led to higher water level even some times the streamflow is small. Human should adjust his activity to enhance his adaptive capacity to flood hazard in the future.

Effects of urban development in the Puget Lowland, Washington, on interannual streamflow patterns: Consequences for channel form and streambed disturbance

Recovery and protection of streams in urban areas depend on a comprehensive understanding of how human activities affect stream ecosystems. The hydrologic effects of urban development and the consequences for stream channel form and streambed stability were examined in 16 streams in the Puget Lowland, Washington, using three streamflow metrics that integrate storm‐scale effects of urban development over annual to decadal timescales: the fraction of time that streamflow exceeds the mean streamflow (TQmean), the coefficient of variation of annual maximum streamflow (CVAMF), and the fraction of time that streamflow exceeds the 0.5‐year flood (T0.5). Urban streams had low interannual variability in annual maximum streamflow and brief duration of frequent high flows, as indicated by significant correlations between road density and both CVAMF and T0.5. The broader distribution of streamflow indicated by TQmean may be affected by urban development, but differences in TQmean between streams are also likely a result of other physiographic factors. The increase in the magnitude of frequent high flows due to urban development but not their cumulative duration has important consequences for channel form and bed stability in gravel bed streams because geomorphic equilibrium depends on moderate duration streamflow (e.g., exceeded 10% of the time). Streams with low values of TQmean and T0.5 are narrower than expected from hydraulic geometry. Dimensionless boundary shear stress (t*) for the 0.5‐year flood was inversely related to T0.5 among the streams, indicating frequent and extensive bed disturbance in streams with low values of T0.5. Although stream channels expand and the size of bed material increases in response to urban streamflow patterns, these adjustments may be insufficient to reestablish the disturbance regime in urban streams because of the differential increase in the magnitude of frequent high flows causing disturbance relative to any changes in longer duration, moderate flows that establish a stable channel.

Stochastic Modeling of Annual Maximum and Minimum Streamflow of Kelkit Stream

The aim of this study is to determine whether the daily extreme streamflows could be generated by stochastic models. For the study, a linear stochastic model known as either Box-Jenkins or ARIMA was used. A Mann-Kendal nonparametric test was applied to the daily extreme data sequences to examine the existence of trends. This test showed that there was no trend in the daily data sequences. The ARIMA model is referred as ARMA since there was no trend in the data sequences and thus, the non-seasonal differencing operator is equal to zero. By using the graphs of ACF and PACF, alternative ARMA models were determined. The plots of the ACF show that there was no linear dependence between the daily maximum streamflows, whereas a linear dependence was observed between the daily minimum streamflows. Therefore, modeling of daily maximum data sequences was discarded. There are four ARMA models that fulfilled all the diagnostic checks among selected models from the graphs of ACF and PACF for the daily minimum data sequences. But ARMA (1, 0) with a constant was chosen as the best model by considering Schwarz Bayesian Criterion (SBC). In addition, error estimates were also shown that ARMA (1, 0) with a constant was the best model.

Approximate Goodness‐of‐Fit Tests of fitted generalized extreme value distributions using LH moments

Approximate goodness‐of‐fit tests of fitted generalized extreme value (GEV) distributions using LH moments are formulated on the basis of comparison of sample LH kurtosis estimates and theoretical LH kurtosis values of the fitted distributions. These tests are different from those that have been derived for testing the GEV distributions of which parameter values are known a priori. The tests are intended to answer the following questions: Does a fitted GEV distribution describe adequately a given data series? If not, can the GEV distribution function describe adequately the larger events in that data series for use for high quantile estimation? If so, what degree of emphasis on the larger events is needed in order that the GEV distribution becomes acceptable? The use of the GEV distribution in conjunction with the LH moment estimation method and the formulated tests should alleviate the need for finding the “correct” distribution. The tests are evaluated by Monte Carlo simulations using generated samples of both GEV and Wakeby distributions. Applications of the tests to observed annual maximum streamflow data are presented.

Probability Distribution of Annual Maximum, Mean, and Minimum Streamflows in the United States

L-moment diagrams are constructed for annual minimum, average, and maximum streamflows at more than 1,455 river basins in the United States. Goodness-of-fit comparisons reveal that the generalized extreme value (GEV), three-parameter lognormal (LN3) and the log Pearson Type III (LP3) distributions provide good approximations to the distribution of annual maximum flood flows. These results are consistent with other L-moment studies. A World Meteorological Organization survey of 54 agencies in 28 countries reveals that the LN3 distribution is not a standard in any country, GEV is a standard in one country, and LP3 is a standard in seven countries. The time is ripe for agencies and countries to reevaluate their standards with respect to the choice of a suitable model for flood frequency analysis. L-moment diagrams also reveal that among numerous alternatives, the Pearson Type III (P3) distribution provides the best fit to both annual minimum and annual average streamflows.

Regional frequency analysis of annual maximum streamflow drought

A regional frequency analysis of annual maximum streamflow drought was presented as a method for investigating the spatial and temporal variability of droughts. Three geographical regions in New Zealand with different climate and physical properties were used in the study. The annual maximum droughts in terms of severity (total deficit) were identified for 44 sites with at least 20 years of daily flow data using two truncation levels: the mean and 75% of the mean. For both approaches the mean of the standardised annual maximum severity was found to vary with physical and climatic catchment characteristics except for one region, where the severity was almost constant because of very high annual rainfall. The best regional estimates of mean severity were found for the lower truncation level. The severities and the durations of the annual maximum droughts at each site were almost linearly related. L moment statistics showed that two of the three regions were homogeneous, and that the three-parameter log-normal distribution gave the best fit to both severities and durations. A baseflow index integrating the influence of various physical and climatic catchment characteristics on hydrographs was found to be useful in regionalising the mean annual maximum severity and the log-normal distribution, allowing estimation of extreme droughts and droughts in ungauged catchments.

A HYDROLOGIC MODEL FOR LOWER COASTAL PLAIN WATERSHEDS, SOUTHEAST UNITED STATES

A disributed, physically-based, watershed hydrologic simulation model, called COASTAL, has been specifically designed for use on watersheds of low relief where streamflow is supplied predominantly by ground water discharge. To use the model, the watershed is divided into square grid elements that are modeled by the lumped parameter approach. I nput data include daily temperature, daily precipitation, topographic elevation, soil field capacity, soil wilting point, aquifer hydraulic conductivity, aquifer thickness and land use for each grid element and a watershed stream rating curve. One or more years of daily streamflow data are needed to calibrate the model. Yearly correlation coefficients between measured and simulated daily streamflow averaged 0.85 and ranged from 0.70–0.91 in tests of the model using 1957-1964 data for the Hurricane Creek watershed, Georgia. Correlation coefficients between measured and predicted annual, monthly, and annual maximum streamflow for the eight years tested were 0.97, 0.93...

Alteration of Streamflow Characteristics Following Road Construction in North Central Idaho

Effects of logging access roads on seven streamflow variables were monitored on six forested headwater watersheds in north central Idaho. The streamflow variables were annual maximum streamflow, date of maximum streamflow, annual minimum streamflow, annual water yield, and streamflow equaled or exceeded 5% of the year, 25% of the year, and 75% of the year. The watersheds, ranging in area from 28.3 to 147.7 ha, had less than 5% of their area in roads. Two statistically significant (α = 0.05) changes occurred following road construction: an increase in the 25% exceedance flows in one watershed and a decrease in the 5% exceedance flows in another watershed. No significant changes were detected in other flow parameters on any of the watersheds. The results indicate that the hydrologic behavior of small forested watersheds may be altered when only a small area is disturbed by roads.

Morphometry and floods in small drainage basins subject to diverse hydrogeomorphic controls

Morphometric parameters such as drainage density, stream magnitude, and relief ratio are practical measures of flood potential in small (<100 mi2) drainage basins. Stereoscopic interpretation of low‐altitude aerial photographs provides the most accurate maps of basins for generating these parameters. Field surveys of a high‐density limestone basin in central Texas show that 1:24,000 scale topographic maps accurately portray the efficient stream channel system but fail to reveal numerous small gullies that may form portions of hillslope hydrologic systems. Flood potential in drainage basins can be defined by a regional index computed as the standard deviations of the logarithms of the annual maximum streamflows. High potential basins tend toward greater relief, greater drainage density, and thus greater ruggedness numbers than low–flash flood potential watersheds. For a given number of first‐order channels (basin magnitude), flash flood regions have greater ruggedness numbers, indicating higher drainage densities combined with steep hillslopes and stream channel gradients. Transient controls on flood response, such as differences between local rainstorm intensities, appear to be the major influences on hydrographs in areas of moderate dissection and relief. Morphometric parameters for low‐potential flash flood regions )Indiana and the Appalachian Plateau( are better estimators of frequent low‐magnitude runoff events (mean annual flood), while the same parameters correlate better with the maximum flood of record in high‐flood potential regions (central Texas, southern California, and north central Utah).