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ON THE CALCULATION OF MAXIMAL OUTLETS OF SMALL MOUNTAINOUS RIVERS (in Armenian conditions)

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... territory of the Republic of Armenia, the calculation of the maximal ... There is a such pond in Armenia and it is river Marmarik, inflow of river Razdan. ... – PowerPoint PPT presentation

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Title: ON THE CALCULATION OF MAXIMAL OUTLETS OF SMALL MOUNTAINOUS RIVERS (in Armenian conditions)


1
ON THE CALCULATION OF MAXIMAL OUTLETS OF SMALL
MOUNTAINOUS RIVERS (in Armenian conditions)
  • Boris Mnatcakanyan,
  • Kamo Aghababyan, Levon Chilingaryan
  • Institute of Water Problems and Hydrotechnics
  • Yerevan, Armenia
  • E-mail Kaghabab_at_aua.am

2
  • Abstract
  • In mountainous countries with complex
    physical geographical conditions, such as the
    territory of the Republic of Armenia, the
    calculation of the maximal outlets of small
    rivers has a very important practical meaning,
    since these rivers bring mudflows and cause
    serious damage to many branches of economy.
  • The methods used to evaluate the maximal
    outlets are often not accurate enough.
  • We have carried out a comparative research of
    the case study of the Marmarik river with
    application of a number of methods used in Soviet
    times and methods used abroad. The research shows
    that when calculating the maximal outlets of
    small rivers it is more efficient to use the
    formulae or the maps, so far as the values
    calculated with the use of these formulae and
    maps are close to the maximal outlets values
    defined by the rivers with long series of
    measurements.

3
  • For determination of the maximal flow parameters
    at present in Armenia the former Soviet Union
    norms are used. However these norms are not used
    in every complicate physical geographical
    Armenian conditions, particularly, in
    hydrologicaly uninvestigated mountain rivers and
    the acting waterfalls. For the last
    methodological indications and recommendations,
    taking into account local conditions of
    floworganizing are used. For the maximal flow
    calculation it is advisable to use regional
    methods of counting the flows, which are formed
    by intensive precipitations.
  • These methods take into account identifically
    different ways physical, geographical, climatic
    and other factors, which influence on the
    maximal flows formation.

4
  • The working out and using methods in Armenian
    conditions are
  • 1. The method of determination of regional
    parameters and hydrological indicators of the
    maximal flows gives a chance to calculate the
    middle maximal flow for each region. In result of
    the regressional analysis the corresponding
    single formula has received by the methods
    author.

5
  • 2. The method of mudflow determination installs
    the connection between morphometrical parameters
    of the pond, flood precipitations and regional
    climatic factors.
  • For determination of the flood consumtion in
    this method is used the known regional empirical
    formula. According to this formula the maximal
    modulus of mudflow diminishes with the increase
    of water catchment area. The use of this method
    is advisable for the water catchments area no
    more than 1000 km2.

6
  • 3. The method of maximal intensity of flow
    used the connection between maximal flood
    parameters and rain intensity as well as
    connections between coefficient of flood and
    relief parameters. The method is recommended for
    the small water catchments area (less than 200
    km2), belonging to the pond of the river Araks.
  • 4. This method of a flood definition in water
    catchments area more than 200 km2 , seems to be
    most simple. The method uses linear connections
    between a freshet rain with 1 flow rate and
    maximal rate received by an empirical way. The
    coefficients of linear connections are received
    as a result of the observed datas statistical
    analysis.

7
  • 5. The method applied for water catchments
    area with the up to 50 km2 and belonging to the
    pond of river Kur establishes a connection
    between maximal flow and precipitations with the
    same provision. The method takes into account
    morphometric parameters, soil covering and the
    unisual intensity of flood.
  • 6.The other method applied for the water
    catchments area more than 300 km2, establishes a
    connection between maximal consumtion of 5
    provision and by the size of the catchments
    area, similarly a formula of reduction. Empirical
    coefficients of the formula are received as a
    result of statistical analysis.

8
  • Though the described methods are based on certain
    statistical analysis, they give no reliable
    results.
  • The authors group came to such conclusion
    after the work carried out by the order of World
    bank, on recalculation of inflow of 23 large
    reservoirs in Armenia.This method using in
    foreign countries, has given strongly
    overestimated results in comparison with CH uPom.
    For example, the calculated results for river
    Akhurian basin, the largest reservoir of Armenia,
    on the methods of PMP is higher than CH u N-y
    (10400 m3/cek) against (1220 m3/cek).
  • For an estimation of applicabity the first
    best approach has been comparative analysis of
    the results of calculations, made on the basis of
    different normative methods. Of course, such
    calculations should be made for small and well
    investigated river ponds, where the applied
    compared methods are the same according to their
    recommendations. There is a such pond in Armenia
    and it is river Marmarik, inflow of river Razdan.

9
  • Map-Scheme of Marmarik River Basin
  • 1- gauge line Marmarik-Hanqavan, 2 gauge line
    Marmarik Aghavnadzor,
  • 3 gauge line Gomur - Meghradzor

10
  • Actually, this pond hydrologically is rather
    well-investigated. The area of the pond is not so
    large, that why the regional method could be
    applied here.
  • The consumption and hydrographs of maximal
    flow by P0.01, 0.1, 1, 5, 50 provision are
    determined for the calculating river site. For
    the comparative estimation of the methods, beside
    the consumtion of Qp, and their statistical
    characteristics (Cv, Cs, RAUT), another important
    parameter (the reduction indicator n of the flow
    maximal modulus) choosen. The latter is defined
    by the relation Q2 / Q1 ( F2 / F1)n, where
    Q1, Q2 are the quantity of consumtion F1, F2
    are the areas of reservoir, corresponding with
    two sequenced calculated sites of river.

11
Table. Maximal flood parameters of Marmarik river
River site and observed line parameters Parameters Methods Methods Methods Methods Methods
River site and observed line parameters Parameters Moments Likelihoods Grapho-analitical Shower floods Limit intensity of flood
Marmarik-Hanqavan 1957-1994. Cv0.335 Cs0.771 Q17.15m3/s R -0.15 Q0.001 70.0 65.9 - -
Marmarik-Hanqavan 1957-1994. Cv0.335 Cs0.771 Q17.15m3/s R -0.15 Q0.01 55.4 53.5 51.8 147 311
Marmarik-Hanqavan 1957-1994. Cv0.335 Cs0.771 Q17.15m3/s R -0.15 Q0.1 50.2 43.7 43.6 114 240
Marmarik-Hanqavan 1957-1994. Cv0.335 Cs0.771 Q17.15m3/s R -0.15 Q1 39.4 34.4 34.6 84.1 178
Marmarik-Hanqavan 1957-1994. Cv0.335 Cs0.771 Q17.15m3/s R -0.15 Cv 0.437 0.34 0.338 - -
Marmarik-Hanqavan 1957-1994. Cv0.335 Cs0.771 Q17.15m3/s R -0.15 Cs 0.768 1.02 1.02 - -
Marmarik-Hanqavan 1957-1994. Cv0.335 Cs0.771 Q17.15m3/s R -0.15 Cv/Cs 1.76 3 3.01 - -
12
Marmarik-Hanqavan 1942-1987. Cv0.45 Cs1.12 Q39.95m3/s R -0.02 Q0.001 197 297 - - -
Marmarik-Hanqavan 1942-1987. Cv0.45 Cs1.12 Q39.95m3/s R -0.02 Q0.01 164 217 182 298 -
Marmarik-Hanqavan 1942-1987. Cv0.45 Cs1.12 Q39.95m3/s R -0.02 Q0.1 132 162 145 230 -
Marmarik-Hanqavan 1942-1987. Cv0.45 Cs1.12 Q39.95m3/s R -0.02 Q1 100 105 106 170 -
Marmarik-Hanqavan 1942-1987. Cv0.45 Cs1.12 Q39.95m3/s R -0.02 Cv 0.49 0.47 0.50 - -
Marmarik-Hanqavan 1942-1987. Cv0.45 Cs1.12 Q39.95m3/s R -0.02 Cs 1.11 1.88 1.50 - -
Marmarik-Hanqavan 1942-1987. Cv0.45 Cs1.12 Q39.95m3/s R -0.02 Cv/Cs 2.26 4 3 - -
Index of reduction degree P0.01 0.764 0.986 0.885 0.498 -
Index of reduction degree P0.1 0.681 0.922 0.846 0.494 -
Index of reduction degree P1.0 0.656 0.786 0.788 0.495 -
13
  • The results of the calculations show, that the
    quantities of the consumtion with the same
    provisions, made by regional methods, are
    considerably more, than the results made by
    normative methods, admitted by hydrology. The
    difference of the parameters of reduction of flow
    maximal modulus, determined by this methods, is
    also considerable.
  • This analysis, not detailed essentially, shows
    the way of improvement of regional methods and
    its difficulties.

14
  • Conclusions
  • 1.The norms and methods of defining the
    parameters of maximal runoft need to be improved
    and regulated for their use under different
    conditions, scales and certain soluable issues.
  • 2.The improvement of the regional methods is
    possible by means of application of comparatine
    analysis with tested normative methods, which are
    applied for rivers under study.
  • 3.Alongside the improvement of regional methods
    it is crucial to select the structure of
    calculation formulae and reduction coefficient.
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