Converting Depth-Cost Output from the Corps GL-SAND model to SVM
Input Slide 2 Outline Goal of the work Why GL-SAND is not used
directly Specific Steps in the Translation Checking to make sure
the SVM and the GL- SAND estimate costs identically Slide 3 The
concept of navigation benefits Like Hydropower, the intent is to
measure net changes in public welfare, not profit In this case, the
metric is the cost of shipping the same quantity of goods When
water levels are higher, ships can be loaded to greater depths, so
it takes fewer trips to carry the same cargo Slide 4 The SVM Inputs
Buffalo district Corps of Engineers uses a model (GL-Sand) to
calculate how much shipping costs would be reduced if harbors were
dredged more deeply They applied that model, normally used for the
Corps maintenance dredging program, to shipments throughout the
Great Lakes The model produces depth-cost functions by shipment
category The data must be pre-processed so that depths can be
related to water surface elevations depth-cost water surface
elevations. Slide 5 The GL-SAND output The GL-SAND produces comma
separated values for costs for each calendar month for depths
varying from 168 to 408 There are two output file sets shipments
within the U.S. or between U.S. and Canada Shipments within Canada
or between a Great Lakes port and an overseas port Note: Because
Lake Ontario and St. Lawrence Seaway levels are not modeled in the
SVM, trip costs with one port below Erie (Ontario, St. Lawrence
River, all foreign ports) are based on depths to Lake Erie. It is
assumed that the amount of water available at the Ontario, St.
Lawrence or foreign port is more than the depth available on the
Upper Great Lakes. While this wont always be true, assuming its
true should give a true picture of the change in costs between
plans and scenarios since all plans and scenarios will have the
same error. Versions of the SVM up to November 2010 truncated
voyages this way but also made the mistake of using the Ontario or
St. Lawrence port depths as Erie port depths, which may have made
the Erie depth the controlling depth in some cases. This is surely
a small error in calculating net benefits because Erie depths are
nearly identical for all plans and because shipments below Erie are
only a portion of the shipments below Lake St. Clair, but it is
corrected in 2011 SVMs. Slide 6 The GL-SAND output To eliminate the
false port and also address the fact that we cant model water
surface elevations in foreign ports, the dock depths at Lake
Ontario or the St. Lawrence, voyages with a foreign, Lake Ontario
or St. Lawrence port will be re-defined as 999 inches so that they
never drive costs. Slide 7 The SVM Inputs The SVM calculates the
depth at each dock and all the connecting channels in between each
month The ship in this movie jumps to the shallowest reach on this
journey each month, showing that you have to check each segment for
depth each month. (Two ships means its a tie). Slide 8 The SVM
Calculation Simulated monthly water surface elevations are
converted to gage readings for each lake by subtracting low water
datum. Row 24 is the first month, 25 the next, etc. These are later
used to calculate DEPTHS at the origin and destination docks. Slide
9 The SVM Calculation Based on known project depths for the
connecting channels, the connecting channel depths are calculated
from the gage readings. Detroit and St Clair gages are calculated
as the averages of the lakes above and below them, while the three
St. Marys levels are based on 2 river gage calculations and MH
levels (Rock Cut). Slide 10 The SVM Calculation The pre-SVM
processing reduced 3,100 routes (trips between one specific dock to
another specific dock) to 240 sub-routes (a sub-route combines all
trips between two lakes so long as the docks on lake 1 are all at
the same depth and the docks on lake 2 are all on the same depth).
The first sub-route in column Q includes trips between Lake
Superior (5) and Lake Superior (5) (all sub-routes that start and
end on Superior are in Route 1) with docks depths of 300 and 324
inches. Slide 11 The SVM Calculation Each row in CN Costs is a
depth-cost function for one sub-route in one calendar month. Each
sub-route may or may not have shipments in a particular month.
These 12 numbers are used to look for the right depth- cost curve
on the CN Costs worksheet CN Costs For example on this sub-route
coded for route 1, lake 5 to lake 5, dock depths 324 and 336 below
LWD, the costs for shipping when the least depth on the trip is
408is $228,360. That may be the sum of the 408 costs for several
different voyages, even ships and cargoes. Slide 12 The SVM
Calculation The equation for May on this sub-route is =OFFSET('CN
Costs'!$C$2,INDIRECT(CONCATENATE(Q$1,$O28+10)),409-
MIN(MIN(INDIRECT(CONCATENATE(Q$7,ROW(),":",Q$8,ROW())),INDIRECT(CONCATENAT
E(Q$5,ROW()))+Q$9,INDIRECT(CONCATENATE(Q$6,ROW()))+Q$10))) An even
200, 400, etc. means no trips that month. Notice that the May value
is 801 and June is 1002 and down below there are costs for month 5
and 6. Slide 13 May year 1 costs for sub-route 155,300,324
OFFSET('CN Costs'!$C$2,INDIRECT(CONCATENATE(Q$1,$O28+10)),409-
MIN(MIN(INDIRECT(CONCATENATE(Q$7,ROW(),":",Q$8,ROW())),INDIRECT(CO
NCATENATE(Q$5,ROW()))+Q$9,INDIRECT(CONCATENATE(Q$6,ROW()))+Q$10)))
Offset starting from cell C2 on CN Costs C2 is the one that says
January costs Lets break the whole equation down... Slide 14 May
year 1 costs for sub-route 155,300,324 OFFSET('CN
Costs'!$C$2,INDIRECT(CONCATENATE(Q$1,$O28+10)),
409-MIN(MIN(INDIRECT(CONCATENATE(Q$7,ROW(),
":",Q$8,ROW())),INDIRECT(CONCATENATE(Q$5,ROW()))+Q$9,
INDIRECT(CONCATENATE(Q$6,ROW()))+Q$10))) That means OFFSET from
cell C2 on CN Costs 801 rows (the value in cell Q$1 js the letter Q
and $O28 = 5 for May Q(5+10) = Q15 = 801 rows; this gives you the
right sub-route And then offset 105 columns (this is the
complicated part, because it solves for the minimum depth and then
figures out how many columns it has to count over to get it). 409
is one more than the deepest depth on the depth-cost table. So the
column count is 409 minus the minimum of: Minimum (H28:H28) =
connecting channel depth = 9999 D28 (the Superior gage=4) + Q$9
(the East dock depth=300) = 304 D28 (again Superior gage = 4) +
Q$10 (the West dock depth = 324) = 328 409-304 = 105 columns to the
right Q$7=H Q$8=H Q$5=D Q$6=D Slide 15 May year 1 costs for
sub-route 155,300,324 OFFSET from C2 801 rows 105 columns Slide 16
What wasnt covered in this documentation? The process of converting
the GL-SAND model outputs Analysis in the SVM that points to which
sub- routes are driving costs. Some ships ALWAYS have enough depth.
Some ships often have depth problems but they cant be helped by
Superior regulation. And then there must be some that are key, and
those might illuminate our plan formulation efforts because wed
know when and where we need more or less water. To be continued.
Slide 17 Analysis The locations of the minimum depth for ships
passing through the Soo shows where the critical water supply issue
is and may help provide a clue for improving the regulation plan to
create more navigation benefits. This work has just begun.
