270

 The cumulative acreage of water coverage under

primitive conditions is greater than double that under

present conditions in wet years, but there is less

difference in cumulative acreage between the two conditions

in dry years. When a series of three or four dry years

occurs, there is greater cumulative water coverage under

primitive conditions than under present conditions for the

first few years, but about the same regional-scale

hydroperiod under the two conditions for the last year or

two of the drought (Figure 63). This is apparent in the

graph for the years 1954-55, 1955-56, and 1956-57 and for

the years 1963-64, 1964-65, and 1965-66. Fluctuation

between extremes in wet years and dry years is greater

under primitive than under present conditions.

 Figure 64 indicates the net annual change in water in

storage in the soil and substrate and in the ponds,

sloughs, and strands under present and primitive conditions

as simulated by the model. Water in storage is the

difference between the total rain received in a year and

the total water that leaves the system through runoff and

ET. Although values for the two parameters, runoff and ET,

fluctuate more from one year to the next under present

conditions than under primitive conditions, change in

storage is just the opposite. Change in storage fluctuates

less under present conditions. The natural system, without

drainage, is able both to store more water and to release