Ecosystem Services: Lessons From the Past for a Sustainable Future - Biodiversity Conservation and Environmental Change - page 122

(a)

reservoir filling
suggests climate
variation also
contributed to onset
of lower lake levels

1m decline during infilling is
matched or exceeded several
times in the historical record

211.0
210.5
210.0
209.5
209.0
208.5
208.0
207.5
207.0

10 year running
mean

Average of 1968 to 1971 Filling of Williston

Reservoir (1968-1971)

1800 1810 1820 1830 1840 1850 1860 1870 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970

Year

Established:
Ft. Chipewyan/Alberta
1788/1905

(b)

2
0
-2
-4
-6
-8

LIA
Highstand

Medieval
Lowstand

Mid-Holocene
Lowstand

5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0

Age (cal year BP)

-3000 -2500-2000 -1500 -1000 500 0 500 1000 1500 2000

Year (BCE /CE)

Medieval (“flashy” spring freshet;
low summer discharge; very low summer
discharge during eleventh century)
LIA (delayed spring freshet;
sustained high summer discharge)

(c)

Twentieth Century (low spring and
summer discharge)

Future? (“flashy” but low
spring freshet; very low
summer discharge)

spring summer

Time

Figure 6.3 (a) Water-level reconstruction for Lake Athabasca 1810-1970 based on tree ring records. (b)
Lake Athabasca water-level record for the past 5,200 years relative to the twentieth century average,
inferred from C/N. The towns of Fort Chipew yan and the province of Alberta were established in times
of unusually abundant freshwater supply. (c) Evolution of hydrographs for rivers draining the eastern
slopes of the Rocky Mountains over the past millennium and anticipated future, based on assemblage of