REPORT OF INVESTIGATIONS No. 40


 MINERAL CONTENT
 The surface waters of this basin are of exceptionally good quality,
with a mineral content ranging from 11 to 33 ppm, and the water is
slightly acid (pH 5.5 to 5.9). The low mineralization of this water can
be attributed to its flowing through an area of practically insoluble sands
and gravels.
 On September 2, 1961, a chloride-profile run on the Blackwater
River (fig. 32) showed that salt water extended about 59 miles up-
stream. Apparently, the downstream flow of the river causes the salt
water to be funneled in to Wright Basin, this being a course of least
resistance. Unless there was a very high tide accompanied by a low
flow, the salt water would probably not extend much farther upstream
than Wright Basin.

 YELLOW RIVER BASIN
 OCCURRENCE OF WATER
 Yellow River heads in southern Alabama, north of Andalusia and
 Opp. The river flows in a southerly direction, entering Okaloosa County
 north of Crestview. South of Crestview, it is joined by Shoal River, its
 largest tributary. The river then turns southwestward, enters Santa
 Rosa County, and flows southwestward into Blackwater Bay.
 The Yellow River drains 1,365 square miles, of which only 115 are
 in Santa Rosa County. Although only a small percentage of the basin is
 in Santa Rosa County, the entire flow of the river is available to the
 county. The average flow entering Blackwater Bay from the Yellow
 River basin is about 2,500 cfs. This is the second largest flow in the two-
 county area; the flow of Escambia River is the largest. Tides from the
 Gulf of Mexico affect the flow in a large part of the 19-mile reach of
 channel in Santa Rosa County. The main channel winds through a
 heavily wooded, swampy flood plain about 2 miles wide. Several estu-
 arine channels extend into the flood plain from Blackwater Bay. From
 the Okaloosa County line to the mouth, there are several cutoff channels
 that leave the main channel and re-enter farther downstream.

 MINERAL CONTENT
 The water of this basin is low in mineral content (23 to 32 ppm),
 but has color ranging from 10 to 80 units. This color, owing to the river
 flowing through a swampy area, makes the water objectionable for
 many uses. Other than the color, the water is of very good quality.