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                          The method

     The GRS  method  leads  to  decision-making  based  on   the
exploration   of  interdependencies  (trade-off  curves)  between
feasible values of performance criteria.  The main steps  of  the
GRS method are the following:
 1) constructing the set of those criterion values which  can  be
obtained  applying  feasible decisions (so called feasible set in
the criterion space);
 2) visual exploration of the objective trade-off curves  between
pairs of criteria;
 3) choice  of  the  most  appropriate  feasible  combination  of
criterion values (feasible goal);
 4) constructing and visualizing the decision which  should  lead
to the feasible goal.
     Here are some comments to these steps of the method.
Our comments are only relevant to  the  particular  case  of  the
regional system concerning Lotov Lake. Note that it is reasonable
to increase the value of the grain-crops output and  to  decrease
the  values  of  the  water  level  drop  and  of  the  pollution
concentration at the same time.
     The first step is fulfilled automatically by  the  computer.
The information entered must be true.  We have done that for you.
     The second step is the hub of the the GRS method  and  needs
detailed consideration. Suppose, some reasonable value of  grain-
crops production is set. Then, all feasible values of the drop of
the water  level  and  of  the  pollution  concentration  can  be
visualized on the computer monitor in the form  a  colored  image
                     (see figure).  Since  you prefer to decrease
                     both the drop in the  water  level  and  the
                     concentration   of   pollutants,   you   are
                     interested in the  "south-western"  frontier
                     of the image (so called efficient frontier).
                     The form of the efficient frontier shows how
                     much the drop of the water level  should  be
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controlled  in  a  trade-off  for  the  decrement  of   pollution
                     concentration .  Note that  near  the  point
                     "M" of  the figure just a small decrement of
                     the  pollution  must  be  exchanged  for   a
                     substantial  increment  of  the  water level
                     drop.  And vice versa,  near the  point  "P"
                     just a small rise of the water level results
                     in sharp decrement of  pollution.  Near  the
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point "N"  the  increment  of  both  criteria  are  approximately
balanced.  The  efficient  frontier  gives you full visual infor-
mation on objective interdependence between these two criteria.
     Note also   that   the  first  criterion,  i.e.  grain-crops
production,  has a set fixed value in the figure.  To include the
first  criterion  into the study we need to enter a collection of
images for several values of production and then  to  superimpose
one image over another.  To simplify the picture,  we use broader
images, so that the frontier is depicted in the figure by a green
line. The broadened image has the same  efficient  frontier,  but
other frontiers will disappear.
     By  superimposing  of   broadened   images  corresponding to
different grain-crops values we obtain a  picture  given  in  the
                     figure.  The yellow image corresponds to the
                     image given  in  the  previous  figure.  The
                     green one corresponds to  a  smaller  grain-
                     crops output,  and the red image corresponds
                     to a larger grain-crops output.  You can see
                     that the increment of the production results
                     in the contraction of the  broadened  image.
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We then obtain a series of overlapping images.  With the help  of
the graphic you can easily understand the  relation  between  the
reduction of crop production and the improvement of the  environ-
ment (i.e. reducing the water level drop and  reducing  pollution
concentration).
     Note that  you  can  freely  obtain different pictures which
show production - drop and production - concentration trade-offs.
     The information  presented  in the second step gives you the
opportunity to make your decision on criterion values  (step  3).
You   have  to  choose  the  most  appropriate  criterion  values
combination (feasible goal).  Your choice will  depend  upon  the
objective trade-offs between criterion values and your subjective
preferences.  You now have full information about  the  situation
and  are  responsible for choosing the balance between production
and environment.
     The fourth  step  is  the  presentation  of  the  values  of
decision variables which lead you to the  chosen  feasible  goal.
Decision variables are presented to you in the form  of  a  table
and diagrams.
