Appendix D

Effect of reservoir regulation on flood peaks and damages

Columbia River Basin

Water Year	Max Annual Mean Daily Peak1 The Dalles (kcfs)		Damages Prevented ($1 million)		Water Year	Max Annual Mean Daily Peak1 The Dalles (kcfs)		Damages Prevented ($1 million)
	Unreg	Obsrv	Lwr Col2	Col Bsn3		Unreg	Obsrv	Lwr Col2	Col Bsn3
1948	1010	1010	*	*	1976	637	419	15.65	43.08
1949	660	624	0.67	*	1977	276	183	0.00	0.00
1950	823	744	9.80	*	1978	565	313	6.00	30.61R
1951	672	602	0.80	*	1979	482	306	1.50	4.65
1952	579	561	0.34	*	1980	544	341	5.16	15.26R
1953	672	612	1.18	*	1981	579	436	10.91	45.26R
1954	590	560	0.26	*	1982	759	422	15.22	78.62
1955	614	551	0.62	*	1983	732	400	18.48	131.00R
1956	940	823	25.00	37.67	1984	628	376	10.71	107.29
1957	820	705	6.60	11.11	1985	550	274	10.45	23.46
1958	735	593	3.55	7.83	1986	719	388	0.24	72.06R
1959	642	555	0.88	2.6	1987	439	284	0.00	9.09
1960	493	470	0.08	0.58	1988	342	236	0.00	2.74
1961	789	699	6.50	7.7	1989	512	312	6.30	37.10
1962	503	460	0.09	1.79	1990	511	372	1.66	15.75
1963	481	437	0.03	.65	1991	568	348	2.64	101.16
1964	764	662	22.91	22.91	1992	328	232	0.00	0.71
1965	669	520	7.18	7.18	1993	602	382	0.00	81.37
1966	455	396	0.43	0.43	1994	381	224	0.00	11.74
1967	781	622	20.80	20.80	1995	552	296	0.03	61.54
1968	533	404	1.07	1.07	1996	719	456	4.32	227.03R
1969	628	449	5.51	5.51	1997	898	571	48.33	378.64
1970	634	429	6.34	6.34	1998	617	442	1.44	88.09
1971	740	557	25.76	25.76
1972	1053	618	260.49	260.49
1973	402	221	0.52	0.52
1974	1010	590	306.36	306.36
1975	669	423	40.97	40.97

¹ Observed discharges are preliminary values calculated from project data.
² Damages are for the Columbia River below McNary Dam. [Dollar values are for the year of the flood. Willamette excluded.]
³ Totals are damages prevented by major projects above The Dalles during the spring and summer runoff. Damages prevented in Canada and/or by levees and channel improvements are not included.
⁴ Damages are based on the flood of December 1977.
^R Revised

Note: In the Columbia River Basin, unregulated flows are those which would have resulted without regulation by Mica, Libby, Duncan, Arrow Lakes, Hungry Horse, Flathead, Noxon Rapids, Pend Oreille, Grand Coulee, Chelan, Jackson Lake, Palisades, American Falls, Dworshak, run-of-river projects, Grand Coulee pumping, and major irrigation diversions in the Snake and Yakima River Basins.

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