Wyniki wyszukiwania - Biblioteka Nauki

1

Quantifying urbanization-associated changes in terrestrial hydrologic system memory

100%

Fleming S. W.

Acta Geophysica

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2007

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tom Vol. 55, no. 3

359-368

EN

A common feature of watershed urbanization is increased hydrograph ‘flashiness’, whereby river discharge fluctuations grow more erratic. Such changes might be intuitively interpreted as a decrease in watershed-scale hydrologic system memory. Here, I investigate this hypothesis through a paired-catchment experiment. The serial correlation coefficient, a common metric of short-term time series memory, is applied to daily winter streamflow data from urbanizing and rural watersheds in the Puget Sound lowland of Washington State, USA. Statistical comparisons confirm that this metric shows highly significant decreases over time in the catchment undergoing land use change, but not in the control watershed, which remains rural over the hydrometric record. Moreover, the mean serial correlation coefficients are statistically indistinguishable between the two catchments over the early period of record, when both watersheds are largely rural, whereas the system memory is far weaker in the urbanized stream relative to the rural stream over the late period, following land use change in the former. The results appear readily interpretable in terms of the physical hydrologic changes typically associated with urbanization. The serial correlation coefficient thus appears to be an instructive measure of urbanization impacts for small streams in this region.

2

The transport of material by the rivers of the northern slope of the Pomeranian Lake Land to the Baltic Sea

100%

Szymczak E.

Oceanological Studies

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2002

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tom Vol. 31, No. 3-4

85-97

EN

The article presents the results of research on the transport of sediment carried by the rivers of the northern slope of the Pomeranian Lake Land to the Baltic Sea in the years 1961-1980. The research includes rivers flowing into the open sea: Rega, Parseta, Wieprza, Slupia, Lupawa and Leba. The total surface of the basins of the rivers in question amounts to 13825.1 km2. The analysis was conducted on the basis of the data concerning the turbidity and flow of the rivers included in hydrological year-books. The size of the transport of the sediment for respective rivers has been counted and the transport of the wash load was analysed with respect to changing conditions of the streamflow and to physical-geographical features of the basin. The transport of the sediment carried to the sea was estimated (46000 tons) and the participation of the rivers of the northern slope of the Pomeranian Lake Land in the total transport of the river wash load from the catchment area of the Baltic Sea has been estimated (0.63%).

3

Climate Change Impact on the Streamflow for the Nam Ou Catchment, North Laos in the Mekong Basin

100%

Nguyen N. Y. , Kha D. D. , Hat D. T. T.

Journal of Ecological Engineering

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2023

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tom Vol. 24, nr 8

209--217

EN

Southeast Asia, in general, and the Mekong Basin (MB), in particular, with its typically warm and wet climate, face water resource challenges. A deep understanding of the future streamflow is needed to manage water resource successfully. Data scarcity and topographical differences have made it difficult to accurately reproduce the streamflow regime in the sub-catchment of the MB. The main goal of this study was to provide the first assessments of streamflow impacts due to climate change for the Nam Ou Basin, a primary Lao sub-catchment of the MB, employing the most updated Couple Model Intercomparison Project Phase 6 (CMIP6) climate scenarios. The MIKE-NAM (Nedbor Affstromnings Model), the observed hydro-meteorological data, and the Moderate Resolution Imaging Spectroradiometer (MODIS) evaporation were employed. The climate change scenarios showed increases in seasonal and annual river discharges with different magnitudes in the future. The annual streamflow was expected to rise by 0.31%, 16.75%, and 38.31% in the 2040s as well as 23.35%, 32.80%, and 74.82% in the 2080s under three scenarios, respectively. The wet season in the Nam Ou Basin occurs one month earlier. The wet season flows increased by 5.6–76.9%, and the dry season flow showed a contrasting directional change, decreased by 8.4%. The annual peak discharge also exhibited an increase of 3.2–14.6% for the SSP1-1.9 scenario in the mid-century (the 2040s), and end-century (2080s). Those figures are 8.9–19.7% for the SSP2-4.5, and 23.3–48.9% for the SSP5-8.5 scenario, respectively. The study revealed the streamflow variation under the effect of climate change in the Nam Ou Basin, a sub-catchment of the MB, highlighting the need for special consideration in disaster risk mitigation, especially under climate change.

4

Streamflow prediction using data-driven models: Case study of Wadi Hounet, northwestern Algeria

86%

Beddal D. , Achite M. , Baahmed D. , Beddal D. , Achite M. , Baahmed D.

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5

Assessment of the impact of climate change on the freshwater availability of Kaduna River basin, Nigeria

86%

Okafor G. C. , Ogbu K. N.

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6

Frequency analysis of the extreme streamflow by the threshold level method in semi-arid region: Case study of Wadi Mekerra catchment in the North-West of Algeria

86%

Yahiaoui A.

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7

Streamflow prediction using data-driven models: Case study of Wadi Hounet, northwestern Algeria

86%

Beddal D. , Achite M. , Baahmed D.

Journal of Water and Land Development

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2020

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tom no. 47

16--24

EN

Streamflow modelling is a very important process in the management and planning of water resources. However, complex processes associated with the hydro-meteorological variables, such as non-stationarity, non-linearity, and randomness, make the streamflow prediction chaotic. The study developed multi linear regression (MLR) and back propagation neural network (BPNN) models to predict the streamflow of Wadi Hounet sub-basin in north-western Algeria using monthly hydrometric data recorded between July 1983 and May 2016. The climatological inputs data are rainfall (P) and reference evapotranspiration (ETo) on a monthly scale. The outcomes for both BPNN and MLR models were evaluated using three statistical measurements: Nash–Sutcliffe efficiency coefficient (NSE), the coefficient of correlation (R) and root mean square error (RMSE). Predictive results revealed that the BPNN model exhibited good performance and accuracy in the prediction of streamflow over the MLR model during both training and validation phases. The outcomes demonstrated that BPNN-4 is the best performing model with the values of 0.885, 0.941 and 0.05 for NSE, R and RMSE, respectively. The highest NSE and R values and the lowest RMSE for both training and validation are an indication of the best network. Therefore, the BPNN model provides better prediction of the Hounet streamflow due to its capability to deal with complex nonlinearity procedures.

8

Does the karst spring improve fish abiotic habitat in mountain streams?

86%

Rajwa-Kuligiewicz A. , Bojarczuk A.

Journal of Water and Land Development

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2024

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tom no. 62

174--184

EN

Mountain streams constitute challenging habitat for many fish species due to rapid and variable flow, cool temperature, and limited food resources. Groundwaters recharge by karst spring may however mitigate harsh habit conditions of mountain streams providing niches for different fish species. This study aims to assess the suitability of mountain streams, replenished by karst springs, for various fish species like alpine bullhead, European grayling, brown and brook trout. The study was conducted in the Chochołowski Stream in the Western Tatra Mountains, Poland. The assessment of abiotic habitat is based on different characteristics of hydrological and thermal regimes as well as water chemical composition investigated between 01.09.2012 and 31.09.2014. The findings reveal that: 1) downstream variability of habitat abiotic conditions (such as water temperature, flow, water chemical composition) may affect the distribution of fish species, 2) karst springs contribute up to 100% of the stream’s recharge during periods of winter low flow, 3) karstic groundwater reduces the variability and amplitudes of stream water temperature and weaken the periodicity in water temperature associated with daily course of air temperature and solar radiation, 4) groundwaters prevent stream freezing in winter and moderate summer temperatures, 5) increasing mineralisation of water below the spring recharge may positively affect fish distribution. The findings underscore the importance of karst springs in modifying the abiotic conditions of fish habitat in mountain streams.

9

Hybrid wavelet transform - MLR and ANN models for river flow prediction: Case study of Brahmaputra river (Pancharatna station)

86%

Khandekar S. D. , Aswar D. S. , Sabale P. D. , Khandekar V. S. , Bajad M. N. , Khaple S.

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tom Vol. 33, No. 1

69--94

EN

In this research, discrete wavelet transform (DWT) is combined with MLR and ANN to develop WMLR and WANN hybrid models, respectively, for the Brahmaputra river (Pancharatna station) flow forecasting. Daily flow data for the period of 10 year were decomposed (up to fifth level) into detailed and approximation coefficients (using Daubechies wavelets db1, db2, db3, db8 and db10) which were fed as input to MLR and ANN to get the predicted discharge values two days, four days, seven days and 14 days ahead. For all lead times, the WMLR-db10 model was found to be superior as compared to WANN-db1, WANN-db2, WANN-db3, WANN-db8, WMLR-db1, WMLR-db2, WMLR-db3, WMLR-db8 and single MLR and ANN models. During testing period, the values of determination coefficient (R2) and RMSE for WMLR-db10 model for two-, four-, seven- and 14-day lead time were found to be, respectively, 0.996 (751.87 m3·s–1), 0.991 (1,174.80 m3·s–1), 0.984 (1,585.02 m3·s–1), and 0.968 (2,196.46 m3·s–1). Also, it was observed that for lower order wavelets (db1, db2, db3) WANN’s performance was better, and for higher order wavelets (db8, db10) WMLR’s performance was better. Correspondingly, it was observed that all hybrid models’ efficiency increased with increase in the decomposition level.

10

Multifractal description of streamfow and suspended sediment concentration data from Indian river basin

72%

Adarsh S. , Dharan D. S. , Nandhu A. R. , Vishnu B. A. , Mohan V. K. , Wątorek M.

Acta Geophysica

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2020

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tom Vol. 68, no. 2

519--535

EN

This study investigated the multifractality of streamfow data of 192 stations located in 13 river basins in India using the multifractal detrended fuctuation analysis (MF-DFA). The streamfow datasets of diferent river basins displayed multifractality and long-term persistence with a mean exponent of 0.585. The streamfow records of Krishna basin displayed least persistence and that of Godavari basin displayed strongest multifractality and complexity. Subsequently, the streamfow-sediment links of fve major river basins were evaluated using the novel multifractal cross-correlation analysis (MFCCA) method of cross-correlation studies. The results showed that the joint persistence of streamfow and total suspended sediments (TSS) is approximately the mean of the persistence of individual series. The streamfow displayed higher persistence than TSS in 60% of the stations while in majority of stations of Godavari basin the trend was opposite. The annual cross-correlation is higher than seasonal cross-correlation in majority of stations but at these time scales strength of their association difers with river basin.

11

Transformation of rivers streamflow of Belarus

72%

Volchek A. A. , Busko E. G. , Tanas W. , Szymanek M.

Journal of Research and Applications in Agricultural Engineering

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2014

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tom Vol. 59, nr 1

131--137

EN

An estimation of streamflow transformation in rivers of Belarus under present conditions influenced by natural fluctuations of flow and anthropogenic impacts, has been performed. On the whole, no sizeable changes in the annual streamflow have been found. At the time of spring floods, an average decrease in the maximum annual discharge in the territory of Belarus is 43%, while the increase in peak summer-autumn and winter yields are 27% and 36%, respectively.

PL

W artykule przeprowadzono ocenę transformacji wodnego spływu rzek Białorusi w warunkach współczesnych, spowodowanych naturalnymi wahaniami i antropogenicznymi czynnikami. Nie stwierdzono w ocenianym okresie znaczących zmian. Zmniejszenie maksymalnego spływu w okresie wiosennych wylewów średnio na Białorusi nie przekroczyło 43%. Zwiększenie minimalnych letnio-jesiennych i minimalnych zimowych poziomów wodnych wyniosło odpowiednio 27% i 36%.

12

Assessment of the impact of climate change on the freshwater availability of Kaduna River basin, Nigeria

72%

Okafor G. C. , Ogbu K. N.

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tom no. 38

105--114

EN

Changes in runoff trends have caused severe water shortages and ecological problems in agriculture and human well-being in Nigeria. Understanding the long-term (inter-annual to decadal) variations of water availability in river basins is paramount for water resources management and climate change adaptation. Climate change in Northern Nigeria could lead to change of the hydrological cycle and water availability. Moreover, the linkage between climatic changes and streamflow fluctuations is poorly documented in this area. Therefore, this study examined temporal trends in rainfall, temperature and runoff records of Kaduna River basin. Using appropriate statistical tools and participatory survey, trends in streamflow and their linkages with the climate indices were explored to determine their amplifying impacts on water availability and impacts on livelihoods downstream the basin. Analysis indicate variable rainfall trend with significant wet and dry periods. Unlike rainfall, temperature showed annual and seasonal scale statistically increasing trend. Runoff exhibit increasing tendency but only statistically significant on annual scale as investigated with Mann–Kendall trend test. Sen’s estimator values stood in agreement with Mann–Kendall test for all variables. Kendall tau and partial correlation results revealed the influence of climatic variables on runoff. Based on the survey, some of the hydrological implications and current water stress conditions of these fluctuations for the downstream inhabitants were itemized. With increasing risk of climate change and demand for water, we therefore recommend developing adaptive measures in seasonal regime of water availability and future work on modelling of the diverse hydrological characteristics of the entire basin.

PL

Zmiany w prawidłowościach odpływu spowodowały poważne ograniczenia w dostępności wody, problemy ekologiczne w rolnictwie oraz zmiany warunków życia ludzi w Nigerii. Zrozumienie długoterminowej zmienności (w poszczególnych latach i dziesięcioleciach) dostępności wody w basenie rzeki jest ogromnie ważne w zarządzaniu zasobami wodnymi i adaptacji do zmian klimatycznych. Zmiany klimatu w północnej Nigerii mogą doprowadzić do zmian cyklu hydrologicznego i dostępności wody. Ponadto, związki między zmianami klimatu a zmiennym odpływem wody są dla tego obszaru słabo udokumentowane. Z tego powodu w przedstawionych badaniach analizowano czasowe zmiany opadu, temperatury i odpływu wody z basenu rzeki Kaduna. Stosując odpowiednie narzędzia statystyczne i badania ankietowe, badano trendy przepływu wody i ich związki ze wskaźnikami klimatycznymi, aby udokumentować ich rosnący wpływ na dostępność wody i warunki życia mieszkańców w dolnym biegu rzeki. Analiza wykazała zmienność opadów z wyraźnymi okresami suchymi i wilgotnymi. W przeciwieństwie do opadów temperatura cechowała się statystycznie istotnym trendem rosnącym w skali pór roku i lat. Odpływ wykazywał istotną statystycznie rosnącą tendencję tylko w skali roku, co wykazano testem trendu Manna–Kendalla. Wartości estymatora Sena były zgodne z wartościami uzyskanymi z zastosowaniem testu Manna–Kendalla dla wszystkich zmiennych. Wartości tau Kendalla i korelacje cząstkowe wykazały wpływ zmian klimatu na odpływ wody. Na podstawie badań ankietowych wykazano pewne skutki hydrologiczne i aktualne warunki stresu wodnego dla mieszkańców zamieszkujących tereny w dolnym biegu rzeki. Wobec rosnącego ryzyka zmian klimatycznych i zapotrzebowania na wodę zaleca się rozwijanie środków przystosowawczych do sezonowego reżimu dostępności wody i przyszłe prace poświęcone modelowaniu zmiennych cech hydrologicznych całego basenu.

13

Seasonality shift and streamfow fow variability trends in central India

72%

Kuriqi A. , Ali R. , Pham Q. B. , Montenegro Gambini J. , Gupta V. , Malik A. , Linh N. T. T. , Joshi Y. , Anh D. T. , Nam T. V. , Dong X.

Acta Geophysica

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2020

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tom Vol. 68, no. 5

1461--1475

EN

A better understanding of intra/inter-annual streamfow variability and trends enables more efective water resources planning and management for current and future needs. This paper investigates the variability and trends of streamfow data from fve stations (i.e. Ashti, Chindnar, Pathgudem, Polavaram, and Tekra) in Godavari river basin, India. The streamfow data were obtained from the Indian Central Water Commission and cover more than 30 years of mean daily records (i.e. 1972–2011). The streamfow data were statistically assessed using Gamma, Generalised Extreme Value and Normal distributions to under stand the probability distribution features of data at inter-annual time-scale. Quantifable changes in observed streamfow data were identifed by Sen’s slope method. Two other nonparametric, Mann–Kendall and Innovative Trend Analysis methods were also applied to validate fndings from Sen’s slope trend analysis. The mean fow discharge for each month (i.e. January to December), seasonal variation (i.e. Spring, Summer, Autumn, and Winter) as well as an annual mean, annual maximum and minimum fows were analysed for each station. The results show that three stations (i.e. Ashti, Tekra, and Polavaram) demonstrate an increasing trend, notably during Winter and Spring. In contrast, two other stations (i.e. Pathgudem, Chindnar) revealed a decreasing trend almost at all seasons. A signifcant decreasing trend was observed at all station over Summer and Autumn seasons. Notably, all stations showed a decreasing trend in maximum fows; remarkably, Tekra station revealed the highest decreasing magnitude. Signifcant decrease in minimum fows was observed in two stations only, Chindnar and Pathgudem. Findings resulted from this study might be useful for water managers and decision-makers to propose more sustainable water management recommendations and practices.

14

Multi variable calibration of hydrological model in the upper Omo Gibe basin, Ethiopia

72%

Nesru M. , Shetty A. , Nagaraj M. K.

Acta Geophysica

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2020

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tom Vol. 68, no. 2

537--551

EN

The calibration of any hydrological model in any river basin is generally performed using a single hydrological variable. Spatially distributed hydrological modeling provides an opportunity to enhance the use of multi-variable calibration models. The objective of this study is to test the efciency of satellite-based actual evapotranspiration in the HBV hydrological model to render the catchment water balance using multi-variable calibration in the upper Omo-Gibe basin in Ethiopia. Five years (2000–2004) meteorological data, streamfow, and actual evapotranspiration (ETa) based on remote sensing were used for calibration and validation purposes. The performance of the HBV model and the efciency of SEBS–ETa were evaluated using certain calibration criteria (objective function). The model is frst calibrated using only streamfow data to test HBV model performance and then calibrated using a multi-variable (streamfow and ETa) dataset to evaluate the efciency of SEBS–ETa. Both model setups were validated in a multi-variable evaluation using streamfow and ETa data. In the frst case, the model performed well enough for streamfow and poor for ETa, while in the latter case, the performance efciency of SEBS–ETa and streamfow data shows satisfactory to good. This implies that the performance of hydrological models is enhanced by employing multi-variable calibration.

15

Daily streamfow prediction using support vector machine artifcial fora (SVM AF) hybrid model

72%

Dehghani R. , Torabi Poudeh H. , Younesi H. , Shahinejad B.

Acta Geophysica

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2020

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tom Vol. 68, no. 6

1763--1778

EN

Precise estimation of river fow in catchment areas has a signifcant role in managing water resources and, particularly, mak ing frm decisions during food and drought crises. In recent years, diferent procedures have been proposed for estimating river fow, among which hybrid artifcial intelligence models have garnered notable attention. This study proposes a hybrid method, so-called support vector machine–artifcial fora (SVM-AF), and compares the obtained results with outcomes of wavelet support vector machine models and Bayesian support vector machine. To estimate discharge value of the Dez river basin in the southwest of Iran, the statistical daily watering data recorded by hydrometric stations located at upstream of the dam over the years 2008–2018 were investigated. Four performance criteria of coefcient of determination (R2 ), rootmean-square error, mean absolute error, and Nash–Sutclife efciency were employed to evaluate and compare performances of the models. Comparison of the models based on the evaluation criteria and Taylor’s diagram showed that the proposed hybrid SVM-AF with the correlation coefcient R2 = 0.933–0.985, root-mean-square error RMSE = 0.008–0.088 m3 /s, mean absolute error MAE = 0.004–0.040 m3 /s, and Nash-Sutclife coefcient NS = 0.951–0.995 had the best performance in estimating daily fow of the river. The estimation results showed that the proposed hybrid SVM-AF model outperformed other models in efciently predicting fow and daily discharge.

16

Improving ANN based streamfow estimation models for the Upper Indus Basin using satellite derived snow cover area

58%

Hassan M. , Hassan I.

Acta Geophysica

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2020

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tom Vol. 68, no. 6

1791--1801

EN

The mountainous catchments often witness contrasting regimes and the limited available meteorological network creates uncertainty in both the hydrological data and developed models. To overcome this problem, remotely sensed data could be used in addition to on-ground observations for hydrological forecasting. The fusion of these two types of data gives a better picture and helps to generate adequate hydrological forecasting models. The study aims at the improvement of ANN-based streamfow estimation models by using an integrated data-set containing, the satellite-derived snow cover area (SCA) with on-ground fow observations. For this purpose, SCA of three sub catchments of Upper Indus Basin, namely Gilgit, Astore and Bunji coupled with their respective gauge discharges is used as model inputs. The weekly stream-fow models are developed for infows at Besham Qila located just upstream of Tarbela dam. The data-set for modeling is prepared through normal izing all variables by scaling between 0 and 1. A mathematical tool, Gamma test is applied to fuse the inputs, and a best input combination is selected on the basis of minimum gamma value. A feed forward neural network trained via two layer Broyden Fletcher Goldfarb Shanno algorithm is used for model development. The models are evaluated on the basis of set of performance indicators, namely, Nash–Sutclife Efciency, Root Mean Square Error, Variance and BIAS. A comparative assessment has also been made using these indicators for models developed, through data-set containing gauge discharges, only and the data-set fused with satellite-derived SCA. In particular, the current study concluded that the efciency of ANN-based streamfow estimation models developed for mountainous catchments could be improved by integrating the SCA with the gauge discharges.

17

Complexity analyses of Godavari and Krishna river streamflow using the concept of entropy

58%

Singh R. K. , Jain M. K.

Acta Geophysica

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2021

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tom Vol. 69, no. 6

2325--2338

EN

The hydrological regime in both the Godavari and Krishna River has been altered due to both human-induced and environmental changes. The present study utilizes the sample entropy and its more generalized approach known as multiscale entropy to investigate the temporal and spatial distribution of complexity and quantify them using SampEn values. Daily streamflow for five stations, three from Godavari River (Dhalegaon, Nowrangpur, and Polavaram), and two from Krishna River (Yadgir and K. Agraharam), was analysed for the complexity analyses. Trends in the streamflow for the selected gauging stations and their annual entropy values have also been evaluated using the Mann–Kendall test. The trend results revealed that three (Dhalegaon and Nowrangpur in Godavari basin and Yadgir in Krishna basin) out of five stations showed significant decreasing trends for both monthly and annual streamflow series. The declining trend in streamflow could be attributed to both anthropogenic (reservoir operation, increased water abstraction, etc.) and climatic (change in monsoon rainfall, temperature, etc.) factors. The most significant reduction in annual streamflow during the post-impact period was observed at Dhalegaon station in Godavari Basin (from 53,573 to 19,555 m3/s) signifying maximum alteration in annual flow regime. The entropy analysis results of streamflow showed that there was obvious spatial and temporal variation in the complexity, as indicated by the annual SampEn values. Although not profound, a negative correlation exists between the annual runoff and SampEn values (highest −0.42 at K. Agraharam) and hence a reverse correspondence exists between them. In MSE analysis, the original streamflow series increased with time scale (up to 30 days was chosen for this study), whereas entropy decreased with an increased time scale. Due to the fully operational state of the dams upstream of the gauging stations, the entropy values during the post-impact period were less the pre-impact period. The present study can be used as a scientific reference to use information science to detect hydrologic alterations in the river basins. Future studies should focus on considering both climatic and land-use changes in conjunction with the human-induced changes for more comprehensive river system disorder analysis.

18

Frequency analysis of the extreme streamflow by the threshold level method in semi-arid region: Case study of Wadi Mekerra catchment in the North-West of Algeria

58%

Yahiaoui A.

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tom no. 41

139--145

EN

Extreme streamflow drought is the direct problem of serious on damaging and on social impacts, so the frequency analysis of hydrological drought is an important work can be done to studying the drought phenomenon in catchments. So the hydrometric data for a river conducts to the establishment of the flow duration curve (FDC) as an important index of streamflow drought regime, from this characteristic, a threshold level can be defined for both perennial or intermittent streams. Well, two partial duration series can be derived for each year; the deficit volume and drought duration series. In the catchment of Wadi Mekerra in the North-West of Algeria, the minimum value estimated from the Pareto’s annual maximum instantaneous flood population (0.60 m3∙s–1) is considered as the threshold level index where, the largest deficit volume and the largest drought duration occurring in a given year are taken into consideration. Hence, the frequency analysis of the streamflow drought regime of the catchment is analysed with Weibull distribution for both deficit volume and drought duration combined with the probability of occurrence which is determined under some criterion in order to forecasting the streamflow drought in the catchment.

PL

Skrajnie niski przepływ w rzece wywołuje poważne, szkodliwe dla środowiska i społeczeństwa skutki, dlatego analiza suszy jest ważnym zadaniem w celu poznania zjawiska w skali zlewni. Dane hydrometryczne rzeki prowadzą do ustalenia krzywych natężenia przepływu (FDC) jako ważnego wskaźnika reżimu przepływu w warunkach suszy. Korzystając z tych charakterystyk, można zdefiniować wartość progową, zarówno dla cieków stałych, jak i dla okresowych. Dla każdego roku można wyprowadzić dwie cząstkowe serie trwania przepływu: serię deficytu objętości i serię trwania suszy. W zlewni Wadi Mekerra w północnozachodniej Algierii minimalna wartość oszacowana na podstawie rocznej populacji Pareto maksymalnych chwilowych powodzi jest traktowana jako wskaźnik wartości progowej, w związku z czym bierze się pod uwagę największy deficyt objętości i najdłuższe trwanie powodzi w danym roku. Analizę częstotliwości przepływu w warunkach suszy w zlewni przeprowadza się w celu prognozowania przepływu w warunkach suszy w zlewni. Wykorzystuje się do tego rozkład Weibulla, zarówno w odniesieniu do deficytu objętości, jak i czasu trwania suszy w powiązaniu z prawdopodobieństwem wystąpienia, które oznacza się, przyjmując pewne założenia.