Name:________________________________________________ Section:________________

Part 1: Soil Moisture Budget Tables and Graphs

1. Complete the water budget below for Stevens Point, Wisconsin (Table 9.4), a location with a rather different climate than Vancouver. Start calculations in the month following the black background and bold white ST value. Refer back to the sections above explaining the calculations for the Vancouver example whenever necessary. Remember to include the signs in the P-PE and DST blanks!

TABLE 9.4 Soil Moisture Budget for Stevens Point, Wisconsin

	Stevens Point, Wisconsin					45°N/90°W		Elev. 329 m				Fine sand			Field capacity = 102 mm
		JAN	FEB	MAR	APR		MAY		JUN	JUL	AUG		SEP	OCT		NOV	DEC	YR
P		28	27	47	70		99		99	90	100		102	60		57	34	812
PE		0	0	0	31		65		91	106	98		72	41		5	0	509
P-PE		+28	+27	+47	+39		+34		+8	-15	+2		+29	+18		+52	+34
DST		0	0	0	0		0		0	-15	+2		+13	0		0	0
ST		102	102	102	102		102		102	87	89		102	102		102	102
AE		0	0	0	31		65		91	105	98		72	41		5	0	509
D		0	0	0	0		0		0	0	0		0	0		0	0	0
S		28	27	47	39		34		8	0	0		16	18		52	34	303

2. Does Stevens Point have a wet or dry climate? How did you know?

Wet. Annual P > annual PE

3. September's P-PE is +30, but only 13 of this returns to the soil as DST.

a. How much of the 30 mm do we still need to account for? 16 mm

b. Where does this excess moisture go in September? To Surplus (runoff into streams)

4. a. What soil moisture season occurs for three quarters of the year in Stevens Point?

Surplus

b. What soil moisture season occurs in July at Stevens Point?

Utilization

5. In Figure 9.2, which site has the shortest duration (horizontal extent of shading) of runoff during surplus? Boulder (only 1.5 months)

6. In Figure 9.2, which site has the highest intensity (vertical extent of shading) of runoff during surplus? Vancouver (in December)

7. Seemingly at odds with what its graph indicates, there is a creek running through Boulder that has flooded several times in the months of July and August. How can this possibly occur, since Boulder receives insufficient precipitation in July and August to have runoff? Where could the floodwater come from? [Hint: consult a map of Colorado topography]

Boulder Creek is what we call an “exotic stream”. The water comes from elsewhere, not from local precipitation; in this case, from the high Rocky Mountains just west of Boulder.

8. Suppose Stevens Point experienced an unusual drought that started in July and lasted through the following February, and that during this time, Stevens Point received no precipitation whatsoever. If normal precipitation resumed in March, why would a drought not necessarily occur the following summer? The total precipitation for March through June is 315 mm, while the total PE for the same period is only 187 mm. The extra 128 mm of moisture, which normally would leave the site as runoff, instead would entirely replenish the soil to its 102 mm field capacity. While a drought would not occur, stream levels would be much lower because they would receive no moisture until June.

9. a. Viewing the maps in Figure 9.3, what states or provinces have the largest differences between annual PE and annual AE? California, Arizona, Sonora

b. What do the Annual P and Annual D maps in Figure 9.3 indicate as occurring in these areas? low precipitation and large deficit; this is a desert

c. Which of the five cities shown in Figure 9.3 has the largest difference between annual PE and AE? Refer to their tables (Tables 9.3, 9.4, 9.5a, 9.6, 9.7).

Boulder

d. Using the graphs in Figure 9.2, does the city you listed as an answer to part (c) also have the precipitation and deficit conditions that best match your answer to part (b)? yes

Figure 9.2 Soil Moisture Budget Graphs (Fine Sand for All Sites)

Figure 9.3 Annual Soil Moisture Budget Variables Maps for North America (in mm/yr)

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part 2: Comparative Field Capacities

1. Complete the first water budget below for Houston, Texas (Table 9.5a). Notice differences occur by changing the soil texture. The first ledger is for fine sand, and the second is for silty loam. Start your calculations in the month following the black background and bold white ST.

TABLE 9.5 Two Soil Moisture Budgets for Houston, Texas

	30°N/095°W				Elevation 19 m				Fine sand				Field capacity = 102 mm
		JAN	FEB	MAR		APR	MAY	JUN		JUL	AUG	SEP		OCT	NOV	DEC	YR
P		103	89	78		89	133	131		105	118	130		93	124	93	1286
PE		20	27	46		76	109	146		163	164	131		88	46	25	1041
P-PE		+83	+62	+32		+13	+24	-15		-58	-46	-1		+5	+78	+68
DST		0	0	0		0	0	-15		-58	-29	0		+5+5	+78	+19
ST		102	102	102		102	102	87		29	0	0		55	83	102102
AE		20	27	46		76	109	146		163	147	130		88	46	25	1023
D		0	0	0		0	0	0		00	17	1		0	0	00	18
S		83	62	32		13	24	0		0	0	0		0	0	49	263

	30°N/095°W				Elevation 19 m				Silty Loam				Field capacity = 203 mm
		JAN	FEB	MAR		APR	MAY	JUN		JUL	AUG	SEP		OCT	NOV	DEC	YR
P		103	89	78		89	133	131		105	118	130		93	124	93	1286
PE		20	27	46		76	109	146		163	164	131		88	46	25	1041
P-PE		+83	+62	+32		+13	+24	-15		-58	-46	-1		+5	+78	+68
DST		0	0	0		0	0	-15		-58	-46	-1		+5	+78	+37
ST		203	203	203		203	203	188		130	84	83		88	166	203
AE		20	27	46		76	109	146		163	164	131		88	46	25	1041
D		0	0	0		0	0	0		0	0	0		0	0	0	0
S		83	62	32		13	24	0		0	0	0		0	0	31	245

2. Silty loam is a finer texture than fine sand. What effect does finer soil texture have on annual deficit? Finer texture’s greater field capacity reduces, or in Houston’s case eliminates, deficit. Essentially, finer texture means a larger soil moisture “savings account”.

3. a. Which Houston soil texture should experience lower stream stage levels, lake levels, and water tables, and probably somewhat greater forest fire risk in summer (April-Sept)? Fine sand, which dries [NcH1] faster because of its lower field capacity.

b. How did you know which soil texture to pick? The texture having the larger deficits.

4. a. What effect does finer soil texture have on the amount of annual AE in Houston? Finer texture (silty loam) increased the annual AE.

b. Why? The finer texture’s greater field capacity enabled more utilization of soil moisture, and thus eliminated the deficit.

5. a. Evapotranspiration includes water yielded to the atmosphere by plant growth during the summertime (April-Sept growing season). Assuming that the plant-generated proportion of AE is constant, which Houston soil texture should have slightly better vegetation growth? The silty loam

b. Why? Slightly greater AE and the elimination of all D

6. Why are coarse soils more hydrologically responsive (flood and dry more rapidly) than fine soils? Lower field capacity means less moisture-holding ability in wet conditions, and more rapid utilization of the lesser moisture “savings” during dry conditions.

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part 3: Latitude, Altitude, and Continentality

Washington DC (Table 9.6) and Boulder, CO (Table 9.7) are at the same latitude, but they have very different water budgets. Notice, however, that two other dimensions of environmental variability are also very different between these cities. Boulder is well over a kilometer higher in altitude than Washington DC. Boulder also has much more interior continentality, being far in the interior of North America and thus well removed from any oceans.

TABLE 9.6 Soil Moisture Budget for Washington, DC

	39°N/077°W				Elevation 3 m				Fine sand				Field capacity = 102 mm
		JAN	FEB	MAR		APR	MAY	JUN		JUL	AUG	SEP		OCT	NOV	DEC	YR
P		70	66	90		72	94	80		97	104	85		78	76	79	991
PE		1	4	22		47	80	116		135	129	99		56	28	7	724
P-PE		+69	+62	+68		+25	+14	-36		-38	-25	-14		+22	+48	+72
DST		0	0	0		0	0	-36		-38	-25	-3		+22	+48	+32
ST		102	102	102		102	102	66		28	3	0		22	70	102
AE		1	4	22		47	80	116		135	129	88		56	28	7	713
D		0	0	0		0	0	0		0	0	11		0	0	0	11
S		69	62	68		25	14	0		0	0	0		0	0	39	278

TABLE 9.7 Soil Moisture Budget for Boulder, CO

	40°N/105°W				Elevation 1638 m				Fine sand				Field capacity = 102 mm
		JAN	FEB	MAR		APR	MAY	JUN		JUL	AUG	SEP		OCT	NOV	DEC	YR
P		14	20	40		65	78	48		47	38	39		38	25	29	481
PE		0	3	14		36	61	90		109	104	78		47	17	2	561
P-PE		+14	+17	+26		+29	+17	-42		-62	-66	-39		-9	+8	+27
DST		+14	+17	+26		+18	0	-42		-60	0	0		0	+8	+27
ST		49	66	92		102	102	60		0	0	0		0	8	35
AE		0	3	14		36	61	90		107	38	39		38	17	2	445
D		0	0	0		0	0	0		2	66	39		9	0	0	116
S		0	0	0		19	17	0		0	0	0		0	0	0	36

1. Which variable (P, PE, AE, D, or S) has the greatest difference between these two sites in annual total? P

2. Since Boulder does get precipitation, why is there rarely any surplus? The atmospheric demand for moisture (PE) greatly exceeds the supply of it (P)

3. Why are PE and AE consistently lower in Boulder than in Washington? PE is lower because Boulder’s higher elevation has lower temperatures. AE is lower at Boulder because the continental interior location has less availability of moisture.

4. Vancouver (Table 9.3) and Stevens Point (Table 9.4) are at about the same latitude, but differ by altitude and continentality. Comparing these two sites, annual S differs greatly between these sites. Why? If the annual AE is very similar and the field capacity is the same, all the extra P has nowhere else to go except rivers and streams (S).

5. Houston (fine sand) (Table 9.5a) and Vancouver (Table 9.3) are both coastal cities at low elevation, but sixteen degrees of latitude separate them.

a. Which variable has the greatest difference between these two sites in annual total? AE

b. Comparing Houston to Vancouver, how much lower does AE get with higher latitude? 500 mm less

c. Comparing Houston to Vancouver, why does PE get lower with higher latitude? Higher latitudes usually have lower temperatures.

part 4: Monsoonal Soil Moisture budgets

1. Complete the water budget table for sandy loam in Kolkata (Calcutta), India (Table 9.8). Start all calculations in the month following the black background and bold white ST.

TABLE 9.8 Soil Moisture Budget for Kolkata, India

	Kolkata, India				23°N/089°E			Elev. 5 m			Sandy loam			Field capacity = 152 mm
		JAN	FEB	MAR		APR	MAY		JUN	JUL		AUG	SEP		OCT	NOV	DEC	YR
P		12	25	32		53	129		291	329		338	266		131	21	7	1634
PE		44	73	152		220	234		212	186		182	184		156	89	47	1779
P-PE		-32	-48	-120		-167	-105		79	143		156	82		-25	-68	-40
DST		-19	0	0		0	0		+79	+73		0	0		-25	-68	-40
ST		0	0	0		0	0		79	152		152	152		127	59	19
AE		31	25	32		53	129		212	186		182	184		156	89	47	1326
D		13	48	120		167	105		0	0		0	0		0	0	0	453
S		0	0	0		0	0		0	70		156	82		0	0	0	308

2. Draw the water budget graph (showing soil moisture seasons) for Kolkata.