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1

Runoff Estimation for the Central Region of the Lesser Zab River Watershed Using the SCS-Curve Number Method and GIS

Salman Qasim Mohammed Khudair, Hamdan Ahmed Naseh Ahmed

Journal of Ecological Engineering

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2023

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Vol. 24, nr 9

232--245

EN

This study aimed to develop a hydrologic model for the central region (central catchments) located between Dokan and Al-Dibis dams in the Lesser Zab River (LZR) watershed, in Iraq. The hydrologic structure of the study area was prepared based on the DEM layer with 12.5 m spatial resolution by using the GIS environment, and then the HEC-HMS software was used for simulating the main hydrological processes like the infiltration losses, transformation, channel routing, and the baseflow contribution by using the SCS-CN, SCS-UH, Muskingum, and the Recession methods respectively. The corrections of the CN parameter due to the effects of the slope and initial abstraction were used and the resulting CN values for the entire LZR watershed were ranging from 56 to 100. This study concluded the effectivity of using the GIS environment and HEC-HMS software in the continuous rainfall-runoff modelling and achieved very good performance with R2 and NSE criteria of 0.9115 and 0.9 under the calibration phase, while 0.925 and 0.91 values were achieved for the same criteria under the validation phase respectively, also the CN was the most sensitive parameter in the proposed hydrologic model.

2

Clarifcation of issues and long-duration hydrologic simulation SCS-CN-based proxy modelling

Aragaw Henok Mekonnen, Mishra Surendra Kumar

Acta Geophysica

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2022

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Vol. 70, no 2

729--756

EN

The aims of this paper are to (I) clarify some issues related to the popular rainfall–runoff SCS-CN (Soil Conservation Service Curve Number) methodology and (II) propose enhanced SCS-CN inspired models for simulation of long-duration (viz., bimonthly, monthly, seasonally, and annually) rainfall-generated runoff and compares its performance with the existing SCS-CN models and Mishra and Singh 1999 model. Issues of SCS-CN are: (a) both C (runoff coefficient) and CN (curve number) with P (rainfall) in contrast to that exhibited by field data, (b) F (infiltration) with Q (direct runoff), (c) Ia (initial abstraction) with S (potential maximum retention), and (d) CN that is also taken as an index of runoff potential. The performance of the proposed SCS-CN inspired models (M3-M8), the existing SCS-CN models (M1 and M2), Mishra and Singh 1999 model (M9), and a special case of M9 that hypothesizes that initial abstraction coefficient (λ)=0 (M10) are tested using rainfall–runoff data of four different agro-climatic river basins in Ethiopia. The performance of the models is evaluated using three statistical criteria involving NSE, RSR, and PBIAS. The resulting high NSE values and lowest RSR and PBIAS for the proposed models reveal that proposed models performed better to different (majority) duration datasets than the existing models. Similarly, the proposed models, when employed to the observed datasets of different timescales, performed satisfactorily in both calibration and validation for all watersheds, underlining the efficacy of the proposed models in field applications.

3

The use of asymptotic functions for determining empirical values of CN parameter in selected catchments of variable land cover

Wałęga A., Młyński D., Wachulec K.

Studia Geotechnica et Mechanica

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2017

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Vol. 39, nr 4

111--120

EN

The aim of the study was to assess the applicability of asymptotic functions for determining the value of CN parameter as a function of precipitation depth in mountain and upland catchments. The analyses were carried out in two catchments: the Rudawa, left tributary of the Vistula, and the Kamienica, right tributary of the Dunajec. The input material included data on precipitation and flows for a multi-year period 1980-2012, obtained from IMGW PIB in Warsaw. Two models were used to determine empirical values of CNobs parameter as a function of precipitation depth: standard Hawkins model and 2-CN model allowing for a heterogeneous nature of a catchment area. The study analyses confirmed that asymptotic functions properly described P-CNobs relationship for the entire range of precipitation variability. In the case of high rainfalls, CNobs remained above or below the commonly accepted average antecedent moisture conditions AMCII. The study calculations indicated that the runoff amount calculated according to the original SCS-CN method might be underestimated, and this could adversely affect the values of design flows required for the design of hydraulic engineering projects. In catchments with heterogeneous land cover, the results of CNobs were more accurate when 2-CN model was used instead of the standard Hawkins model. 2-CN model is more precise in accounting for differences in runoff formation depending on retention capacity of the substrate. It was also demonstrated that the commonly accepted initial abstraction coefficient λ = 0.20 yielded too big initial loss of precipitation in the analyzed catchments and, therefore, the computed direct runoff was underestimated. The best results were obtained for λ = 0.05.

4

Direct runoff assessment using modified SME method in catchments in the Upper Vistula River Basin

Wałęga A., Rutkowska A., Grzebinoga M.

Acta Geophysica

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2017

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Vol. 65, no. 2

363--375

EN

Correct determination of direct runoff is crucial for proper and safe dimensioning of hydroengineering structures. It is commonly assessed using SCS-CN method developed in the United States. However, due to deficiencies of this method, many improvements and modifications have been proposed. In this paper, a modified Sahu–Mishra–Eldo (SME) method was introduced and tested for three catchments located in the upper Vistula basin. Modification of SME method involved a determination of maximum potential retention S based on CN parameter derived from SCS-CN method. The modified SME method yielded direct runoff values very similar to those observed in the investigated catchments. Moreover, it generated significantly smaller errors in the direct runoff estimation as compared with SCS-CN and SME methods in the analyzed catchments. This approach may be used for estimating the runoff in uncontrolled catchments.

5

Assessment of Retention Potential Changes as an Element of Suburbanization Monitoring on Example of an Ungauged Catchment in Poznań Metropolitan Area (Poland)

Mrozik K.

Rocznik Ochrona Środowiska

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2016

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Tom 18, cz. 1

188--200

PL

Rozwój miast skutkuje znacznymi zmianami użytkowania terenu i powiązań funkcjonalnych pomiędzy obszarami miejskimi i wiejskimi. Zmieniające się relacje pomiędzy użytkowaniem obszarów miejskich i wiejskich prowadzą do zmian jakości życia mieszkańców, środowiska i świadczeń ekosystemów, w tym zasobów wodnych. Zmiany te są najbardziej widoczne na obszarach podmiejskich. Różne scenariusze rozwoju obszarów zurbanizowanych w Europie oparte na założeniach IPCC wskazują niezależnie na ich dalszą ekspansję w granicach 0,4-0,7% rocznie, co jest wynikiem ponad dziesięciokrotnie wyższym niż rozwój jakichkolwiek innych typów użytkowania. Oznacza to, że nasilenie tego procesu będzie szczególnie widoczne na obszarach podmiejskich, w tym na znacznych obszarach Polski. Obserwowane intensywne przekształcania terenów użytkowanych rolniczo na tereny zabudowane i zurbanizowane zmuszają do zastanowienia się nad wpływem suburbanizacji na gospodarowanie wodami zwłaszcza w kontekście zjawisk ekstremalnych, z których w Polsce w ostatnich dwóch dekadach szczególnie dotkliwe okazały się powodzie w 1997, 2001 i 2010 r. Szczególnego znaczenia nabiera potrzeba monitoringu zjawiska suburbanizacji w kontekście jej wpływu na gospodarowanie wodą w zlewni rzecznej będącej zgodnie z zasadą IWRM podstawową jednostką planistyczną w planowaniu w gospodarowaniu wodami. Celem pracy była ocena możliwości zastosowania metody SCS-CN jako elementu monitoringu procesu suburbanizacji poprzez zwymiarowanie zmian w potencjalne retencyjnym niekontrolowanych zlewni rzecznych na terenach podmiejskich w miejskich obszarach funkcjonalnych (metropolitalnych). Szczegółowe analizy w pracy wykonano na przykładzie zlewni Skórzynki położonej w granicach gmin wiejskich Dopiewo i Tarnowo Podgórne i miasta Poznań stanowiących rdzeń Poznańskiego Obszaru Metropolitanego (POM) (określanego obecnie jako Miejski Obszar Funkcjonalny Ośrodka Wojewódzkiego) Ogółem według delimitacji zaproponowanej przez Wielkopolskie Biuro Planowania Przestrzennego POM obejmuje 45 gmin wraz z Poznaniem (w tym 15 miast powiatowych i 15 pozostałych miast). Do oceny zmian potencjału retencyjnego i opadu efektywnego wykorzystano metodę SCS-CN. Zmiany zagospodarowania terenu oceniono na podstawie mapy topograficznej z 1998 r. w skali 1: 10 000 oraz urban atlasu bazującego na zdjęciach satelitarnych SPOT5 o rozdzielczości terenowej 2,5m z roku 2007. Dane dotyczące gleb pochodziły z mapy glebowo-rolniczej w skali 1: 25 000 wykonanej przez IUNG w Puławach. Wszystkie analizy wykonano przy użyciu oprogramowania ArcGIS 10.0 firmy ESRI. Dane opadowe pochodziły ze stacji Poznań-Ławica. Dzięki metodzie SCS-CN wykazano dla zlewni Skórzynki w okresie 11 lat dla przeciętnych początkowych warunków wilgotnościowych spadek potencjalnej retencji (o 20%, tj. z 99 na 80mm) oraz wzrost opadu efektywnego (o 17%, tj. z 35 na 41mm) wyliczonego dla ekstremalnego zdarzenia opadowego odnotowanego 17.08.2010 r. Wykonane analizy pozwalają stwierdzić, że metoda SCS-CN jest użytecznym i pożądanym narzędziem monitoringu procesu suburbanizacji w niekontrolowanych zlewniach położonych w obrębie obszarów metropolitalnych w celu oceny zmian potencjału retencyjnego zlewni. Uzyskane wyniki mogą stanowić kryterium decyzyjne dla lokalnych władz we właściwym kreowaniu polityki przestrzennej, zwłaszcza w zakresie kształtowania zasobów wodnych oraz przeciwdziałania lokalnym powodziom i suszom.

EN

The development of the cities results in significant changes in land use and functional connections between urban and rural areas. The changing relations between the use of urban and rural areas lead to changes in the quality of the inhabitants’ lives, of the environment and ecosystem services, including water resources. Those changes are the most visible in peri-urban areas. Different scenarios of the development of urbanized areas in Europe based on the IPCC assumptions indicate their further expansion at 0,4-0,7% per year which is over 10 times higher score than any other land use. This means that the intensity of this process will be particularly visible in peri-urban areas, including considerable areas of Poland. The observed intensive transformations of arable lands into built-up and urbanized areas make one think about the influence of suburbanization on water management, especially in the context of extreme phenomena, out of which the most afflictive over the two last decades were floods in 1997, 2011 and 2010. Monitoring the process of suburbanization gains importance in the context of its influence on water management in the river catchment which, according to the IWRM principle, a basic planning unit are in water management planning. The objective of this paper was evaluation of the possibility of using the SCS-CN method as an element of monitoring process of suburbanization through sizing the changes in the in water retention potential of ungauged catchments on peri-urban areas of metropolitan areas. Detailed analyses were carried out based on the Skorzynka river catchment located within the rural communes of Dopiewo, Tarnowo Podgórne and the city of Poznań which are the nucleus of Poznan Metropolitan Area (PMA) (currently defined as the voivodeship urban functional area of Poznań). Altogether, according to the delimitation proposed by the regional planning office Wielkopolskie Biuro Planowania Przestrzennego (WBPP), PMA comprises 45 communes together with Poznań (including 10 cities – centres of district and 15 other small cities). To the assessment of potential water retention and effective precipitation the SCS-CN method was used. The changes in land use were estimated on the basis of a topographic map from 1998 at a 1:10 000 scale and the Urban Atlas based on satellite photographs from SPOT 5 satellite on the ground resolution of 2.5 m from 2007. Data on soil were obtained from soil and agricultural maps at a 1:25 000 scale performed by Institute of Soil Science and Plant Cultivation (IUNG) in Puławy. All analyses were performed using ArcGIS 10.0 software by ESRI. The information about precipitation based on the data from the climatic station of Poznań Ławica Thanks to using the SCS-CN method a 20% decrease of potential water retention (99 to 80mm) in the 11-years period for Skórzynka catchment in average antecedent moisture conditions (AMC II) has been demonstrated. Also, a 17% increase of effective precipitation (35 to 41 mm) calculated for extreme rainfall event observed on 17/08/2010 was shown. The conducted analyses allow to conclude that the SCS-CN method is a useful and desirable tool used to monitor the process of suburbanization in ungauged catchments located within metropolitan areas in order to assess the changes of potential water retention. The obtained data may be a decision criterion for local authorities in the proper creation of spatial policy, especially in the sphere of water resources management and preventing local floods and droughts.

6

Derivation of the SCS-CN parameter S from linearized Fokker-Planck equation

Mishra S., Singh V.

Acta Geophysica Polonica

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2003

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Vol. 51, nr 2

179-202

EN

The potential maximum retention, S, of the Soil Conservation Service Curve Number (SCS-CN) method (SCS, 1956) was derived for a large set of published infiltration data ranging from Plainfield sand to Yololight clay using the relations between psi (negative pressure) and theta (moisture content) and between K (hydraulic conductivity) and theta. The physical significance of S is explained using the diffusion term of the linearized, Fokker-Planck equation for infiltration, which relates S to the storage and transmission properties of the soil. The s-values exhibit a strong looped relationship with the initial moisture content, analogous to that for curve numbers for three antecedent moisture conditions. The variations of S in vertical infiltration is also explained and discussed.