Exercise 2 – Calculation of Recharge Altitude
Determine the recharge altitude of the Kirstenbosch spring, which is 160 masl, by working through the 4 items listed here.
1. Calculate the mean isotopic composition of the spring water based on the measurements provided in this table.
Stable isotope data for the Kirstenbosch spring
|
date |
δD ∆‰ |
δ18O ∆‰ |
|
|
March 2010 |
-13.7 |
-3.01 |
|
|
November 2010 |
-9.4 |
-3.03 |
|
|
May 2011 |
-12.4 |
-3.71 |
|
|
October 2011 |
-12.9 |
-3.04 |
|
|
May 2012 |
-10.2 |
-3.48 |
|
|
September 2012 |
-10.1 |
-2.37 |
|
2. Calculate the weighted mean stable isotope compositions (ignore missing values) for the University of Cape Town (135 masl) and the Table Mountain Cableway (1074 masl) using the 3-year dataset provided in the table on the following page.
3. Use the weighted means caclulated in item 2 to calculate an altitude effect for Table Mountain.
4. Calculate the recharge altitude of the Kirstenbosch spring.
Stable isotope data for precipitation at UCT and the Table Mountain Upper Cableway Station.
|
|
UCT |
TMC |
|||||
|
|
D ‰ |
δ18O ‰ |
Precipitation mm |
D ‰ |
δ18O ‰ |
Precipitation mm |
|
|
2010 |
J |
+9.7 |
+0.75 |
9 |
|
|
|
|
F |
-5.8 |
-0.54 |
13 |
|
|
|
|
|
M |
+0.4 |
-0.83 |
7 |
|
|
|
|
|
A |
-12.1 |
-2.25 |
45 |
|
|
|
|
|
M |
-8.4 |
-2.78 |
275 |
-15.0 |
-3.14 |
280 |
|
|
J |
-17.0 |
-3.31 |
201 |
-24.4 |
-4.35 |
170 |
|
|
J |
-15.0 |
-3.69 |
166 |
|
|
200 |
|
|
A |
-4.9 |
-1.74 |
121 |
|
|
150 |
|
|
S |
-3.3 |
-2.24 |
101 |
|
|
100 |
|
|
O |
-3.3 |
-2.15 |
103 |
-16.3 |
-3.04 |
120 |
|
|
N |
-6.2 |
-2.39 |
73 |
-13.1 |
-2.65 |
90 |
|
|
D |
-39.9 |
-5.06 |
17 |
-16.0 |
-2.35 |
60 |
|
|
2011 |
J |
-5.2 |
-0.15 |
16 |
-1.2 |
-0.75 |
30 |
|
F |
13.9 |
+3.19 |
3 |
|
|
20 |
|
|
M |
-23.6 |
-4.12 |
16 |
|
|
50 |
|
|
A |
-5.8 |
-2.73 |
111 |
-14.8 |
-4.61 |
90 |
|
|
M |
-12.3 |
-3.69 |
145 |
-14.7 |
-4.17 |
142 |
|
|
J |
-18.3 |
-4.82 |
191 |
-16.9 |
-4.85 |
150 |
|
|
J |
-14.6 |
-4.68 |
49 |
-11.6 |
-4.71 |
70 |
|
|
A |
-3.8 |
-2.63 |
209 |
-14.4 |
-4.64 |
165 |
|
|
S |
-0.1 |
-1.51 |
141 |
-9.2 |
-3.51 |
115 |
|
|
O |
-17.0 |
-3.48 |
41 |
-13.6 |
-3.84 |
100 |
|
|
N |
-12.0 |
-3.21 |
72 |
-17.4 |
-4.64 |
100 |
|
|
D |
-1.6 |
-2.05 |
62 |
-9.6 |
-3.51 |
90 |
|
|
2012 |
J |
+5.4 |
+0.78 |
46 |
-4.7 |
-2.93 |
130 |
|
F |
-2.5 |
-0.68 |
21 |
-1.0 |
-2.05 |
80 |
|
|
M |
-11.9 |
-3.07 |
69 |
-12.9 |
-3.91 |
110 |
|
|
A |
-9.8 |
-3.12 |
133 |
-13.7 |
-4.34 |
130 |
|
|
M |
-10.4 |
-3.08 |
143 |
|
|
155 |
|
|
J |
-6.4 |
-4.15 |
230 |
-8.7 |
-2.32 |
200 |
|
|
J |
-8.8 |
-2.67 |
300 |
-7.6 |
-2.93 |
240 |
|
|
A |
-13.5 |
-3.25 |
214 |
-20.8 |
-4.82 |
145 |
|
|
S |
-10.8 |
-2.36 |
172 |
-22.4 |
-5.75 |
215 |
|
|
O |
-7.1 |
-3.16 |
44 |
|
|
123 |
|
|
N |
+0.1 |
-1.08 |
60 |
|
|
44 |
|
|
D |
+6.9 |
-0.17 |
10 |
|
|
20 |
|
Click for solution to Exercise 2