A. Marshland
requirements |
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A. |
B. |
C |
D |
E |
F |
G |
H |
I |
J |
K |
L |
M |
N |
O |
P |
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King's Park |
Corrected |
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Potential |
Requirement |
Requirement |
Requirement |
Target level |
Yield from |
Requirement |
Requirement |
Requirement |
Requirement |
Target pond |
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Month |
Rainfall |
Rainfall |
Evaporation |
Balance |
cumulative |
to maintain level |
to maintain level |
to maintain level |
(below max) |
change |
for target |
for target |
for target |
for target |
water level |
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mm |
mm |
mm |
mm |
balance mm |
l |
l/day |
l/sec |
mm |
mm |
mm |
l |
l/day |
l/sec |
mPD |
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Jul |
181 |
118 |
151 |
-33 |
0 |
808,110 |
26,068 |
0.30 |
-50 |
-100 |
133 |
3,268,110 |
105,423 |
1.22 |
2.950 |
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Aug |
97 |
63 |
147 |
-84 |
-84 |
2,072,550 |
69,085 |
0.80 |
0 |
-50 |
134 |
3,302,550 |
110,085 |
1.27 |
3.000 |
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Sep |
72 |
47 |
135 |
-88 |
-172 |
2,158,404 |
69,626 |
0.81 |
-75 |
75 |
13 |
313,404 |
10,110 |
0.12 |
2.925 |
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Oct |
14 |
9 |
144 |
-135 |
-307 |
3,317,679 |
110,589 |
1.28
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-200 |
125 |
10 |
242,679 |
8,089 |
0.09 |
2.800 |
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Nov |
9 |
6 |
110 |
-104 |
-411 |
2,555,571 |
82,438 |
0.95
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-300 |
100 |
4 |
95,571 |
3,083 |
0.04 |
2.700 |
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Dec |
64 |
42 |
69 |
-27 |
-438 |
664,323 |
21,430 |
0.25 |
-325 |
25 |
2 |
49,323 |
1,591 |
0.02 |
2.675 |
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Jan |
34 |
22 |
59 |
-37 |
-475 |
910,815 |
32,529
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0.38 |
-350 |
25 |
12 |
295,815 |
10,565 |
0.12 |
2.650 |
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Feb |
1 |
1 |
65 |
-64 |
-539 |
1,572,309 |
50,720 |
0.59 |
-400 |
50 |
14 |
342,309 |
11,042 |
0.13 |
2.600 |
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Mar |
61 |
40 |
68 |
-28 |
-566 |
681,174
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22,706 |
0.26 |
-425 |
25 |
3 |
66,174 |
2,206 |
0.03 |
2.575 |
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Apr |
130 |
85 |
66 |
19 |
-547 |
- |
- |
- |
-425 |
0 |
0 |
- |
- |
- |
2.575
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May |
332 |
216 |
111 |
105 |
-442 |
- |
- |
- |
-400 |
-25 |
0 |
- |
- |
- |
2.600 |
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Jun |
512 |
333 |
97 |
235 |
-207 |
- |
- |
- |
-150 |
-250 |
15 |
363,096
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11,713 |
0.14 |
2.850 |
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Total |
1507.1 |
979.6 |
1219.6 |
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14,740,935 |
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339 |
8,339,031 |
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B. Water
available from station roof |
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A. |
B. |
J = B - RC |
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Month |
LMC rainfall |
Monthly balance |
Runoff volume |
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mm/month |
mm/month |
l |
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Jul |
118 |
112 |
2,682,420 |
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Aug |
63 |
60 |
1,437,540 |
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Sep |
47 |
45 |
1,072,968 |
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Oct |
9 |
9 |
205,998 |
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Nov |
6 |
6 |
134,862 |
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Dec |
42 |
40 |
952,926 |
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Jan |
22 |
21 |
496,470 |
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Feb |
1 |
1 |
13,338 |
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Mar |
40 |
38 |
909,948 |
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Apr |
85 |
80 |
1,926,600 |
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May |
216 |
205 |
4,920,240
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Jun |
333 |
316 |
7,581,912 |
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Total |
980 |
931 |
22,335,222 |
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C. Additional
supply from storage pond |
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Month |
Volume reqd to |
Inputs |
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Losses |
Volume in |
Depth in |
Level in |
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meet target |
Rainfall |
Roof runoff |
evaporation |
storage pond |
storage pond |
storage pond |
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l |
l |
l |
l |
l |
mm |
mPD |
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Jul |
2,975,840 |
258,830 |
2,682,420 |
331,100 |
2,200,000 |
1,000 |
3.00 |
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Aug |
3,007,200 |
138,710 |
1,437,540 |
324,060 |
1,834,310 |
834 |
2.83
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Sep |
285,376 |
103,532 |
1,072,968 |
296,560 |
79,300 |
36 |
2.04 |
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Oct |
220,976 |
19,877 |
205,998 |
316,580 |
673,864 |
306 |
2.31 |
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Nov |
87,024 |
13,013 |
134,862 |
241,560 |
362,183 |
165 |
2.16 |
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Dec |
44,912 |
91,949 |
952,926 |
151,360 |
181,474 |
82 |
2.08 |
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Jan |
269,360 |
47,905 |
496,470 |
129,360 |
1,030,077 |
468 |
2.47 |
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Feb |
311,696 |
1,287
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13,338 |
141,900 |
1,175,732 |
534 |
2.53 |
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Mar |
60,256
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87,802 |
909,948 |
148,720 |
736,761 |
335 |
2.33 |
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Apr |
- |
185,900 |
1,926,600 |
144,320 |
1,525,535 |
693 |
2.69
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May |
- |
474,760 |
4,920,240 |
243,540 |
2,200,000 |
1,000 |
3.00 |
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Jun |
330,624 |
731,588 |
7,581,912 |
214,060 |
2,200,000 |
1,000
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3.00 |
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Total |
7,593,264 |
2,155,153 |
22,335,222 |
2,683,120 |
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WATER BUDGET AND PREDICTED WATER LEVEL CHANGES FOR SAN TIN / LOK
MA CHAU STATION COMPLEX MARSHLAND |
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SOURCE: HONG KONG
OBSERVATORY DATA REFER TO KING'S PARK MONITORING STATION, KOWLOON. |
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WESTERN MARSH WATER BUDGET |
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*Cumulative balance is calculated by setting the water level to
0 at the end of the wet season |
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and at the end of the period when soil is at field capacity (i.e
after which monthly balances are in continual deficit for the dry season) |
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Water levels refer to above ground open water levels |
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Assumptions |
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Rainfall in at Lok Ma Chau
is 65% of that at King's Park (according to Hong Kong Observatory isohyet
data for 1961-90). |
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Evaporation rates do not
significantly differ between King's Park Monitoring Station and Lok Ma Chau |
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Under wetland conditions
evapotranspiration rates from open water, bare soil/mud and wetland
vegetation are approximately equal and equal to observed monthly evaporation
rates. |
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Predicted balances are
based on potential evaporation rates and do not take into account reduced
evaporation when soil water tables are low. |
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Wetland area is constant |
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Seepage rates are minimal |
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Storage pond is full at the
end of the wet season |
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Water level changes below
the soil surface have negligable effects (therefore specific yields when
water levels drop below ground level are not taken into account) |
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MA. Area of marsh
vegetation (excluding western marsh & water treatment reedbed) (ha) = |
2.46 |
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Targets relative to max
operating water level (mPD) |
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3.00 |
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A. Predicted
levels based on mean monthly rainfall over 1990-99 |
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A. |
B. |
C |
D |
E |
J |
P |
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King's Park |
Corrected |
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Max monthly |
Predicted pond |
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Month |
Rainfall |
Rainfall |
Evaporation |
Balance |
level below max |
level below max |
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mm |
mm |
mm |
mm |
mm |
mm |
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Jul |
437 |
284 |
151 |
134 |
-50 |
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Aug |
466 |
303 |
147 |
156 |
0 |
- |
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Sep |
329 |
214 |
135 |
79 |
0 |
- |
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Oct |
136 |
89 |
144 |
-55 |
-50 |
-
55 |
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Nov |
25
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16 |
110 |
-94 |
-100 |
-
144 |
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Dec |
28 |
18 |
69 |
-50 |
-150 |
-
150 |
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Jan |
25 |
16 |
59 |
-42 |
-200 |
-
200 |
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Feb |
73 |
47 |
65 |
-17 |
-250 |
-
250 |
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Mar |
59 |
38 |
68 |
-30 |
-275 |
-
280 |
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Apr |
168 |
109 |
66 |
44 |
-300 |
-
300 |
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May |
240 |
156 |
111 |
45 |
-300 |
-
300 |
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Jun |
477
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310 |
97 |
213 |
-150 |
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Total |
2463.6 |
1601.3 |
1219.6 |
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