draining Kvichak Bay move directly seaward along the 

 northwest side of inner Bristol Bay past Cape Constan- 

 tine. Between Egegik and Ugashik rivers and other rivers 

 entering on the east side of the bay is a region of high- 

 salinity water which has a net movement toward the 

 head of Bristol Bay. Mixing and stirring will cause 

 Egegik and Ugashik river waters entering the east side of 

 the bay to mix with adjacent high-salinity water which 

 has a net movement toward the head of the bay. Thus, 

 the waters of Egegik and Ugashik rivers are carried above 

 their mouths toward the head of the bay by the net cur- 

 rent (Figs. 7, 8), and near Middle Bluff this water joins 

 the flow of less saline water which is transported seaward 

 on the northwest side of the bay. 



On the southeast side toward the head of Bristol Bay 

 and north of the mouth of Ugashik River, inshore water 

 must become a mixture of Ugashik and Egegik river 

 water rather than being largely Ugashik River water. 

 Between the entrance of Egegik Bay and Middle Bluff, 

 river water must be largely of Egegik River origin 

 because it has a greater discharge than Ugashik River. 

 Moreover, Ugashik River water is being diluted by lateral 

 mixing with higher salinity offshore water during trans- 

 port toward the head of the bay. In the Middle Bluff 

 area, Egegik River water should predominate, but some 

 Naknek River water could also be present. Kvichak River 

 water must be well offshore in this area. 



Tidal Influence 



Flood tidal currents carry some Naknek, Egegik, and 

 Ugashik river waters north or above their respective out- 

 lets into Bristol Bay, which cover tideflats exposed at low 

 tide (Fig. 8). 



Naknek River water transported north of the Naknek 

 River mouth by the flood current mixes with Kvichak 

 River water. This mixed water moves seaward on the suc- 

 ceeding ebb tide and should occur just to the west of the 

 boundary marking the interface between water leaving 

 Naknek and Kvichak rivers (Fig. 9). Thus, regardless of 

 the striking separation of these waters shown by shear 

 lines, during ebb tide there should be a gradation from 

 Naknek to Kvichak river water from the southeast side to 

 the northwest side of Kvichak Bay. In addition, there 

 should also be a change from Naknek to Kvichak river 

 water along the coast directly above Naknek River 

 mouth during flood tide. 



Egegik and Ugashik river waters transported north of 

 the entrances to Egegik and Ugashik bays by flood tide 

 (Fig. 8) mix with adjacent coastal waters. This mixture 

 moves seaward on the succeeding ebb tide as part of the 

 coastal water west of the shear line marking the separa- 

 tion of coastal water and waters leaving Egegik and 

 Ugashik bays, respectively (Fig. 7). From the southeast 

 to the northwest side of Bristol Bay in these regions, 

 there should be a change from the coastal water of Egegik 

 and Ugashik origin to high-salinity water, and then to 

 low-salinity water originating from 9 of the 10 major 

 sockeye-salmon-producing rivers entering inner Bristol 

 Bay. 



An additional effect of tidal action on the distribution 

 of river water is apparent in the salinity distribution in 

 the inner bay at low and high tides (Figs. 3-6). The dis- 

 tribution of certain isohalines at low and high tides sug- 

 gests that a portion of the river runoff water that moves 

 seaward from Kvichak Bay may actually be transported 

 into Nushagak Bay at high tide. This river water would 

 be mainly of Kvichak and Naknek origin, but perhaps 

 some would be of Egegik origin. 



Effects of Wind 



My studies were done when wind velocities were 

 generally less than 15 knots, and the effects of prolonged 

 strong winds on the distribution of river waters were not 

 evaluated. Strong winds undoubtedly increase the 

 horizontal mixing between individual river waters and 

 between river water and seawater. Drift cards afloat for 6 

 wk or more assumed a distribution similar to the course 

 inferred from the salinity distribution of the area. The 

 cards must have encountered winds exceeding 30 knots, 

 which suggests that the circulation pattern determining 

 the course followed by all river waters to the northwest 

 side of inner Bristol Bay may not have changed during 

 periods when winds exceeded 15 knots. 



In the summer months, winds in Bristol Bay are 

 generally from the southeast, and because the movement 

 of surface water is to the right of wind direction in the 

 Northern Hemisphere (Sverdrup et al. 1942), these 

 southerly winds move water onshore or toward the head 

 of Bristol Bay. Prolonged periods of strong winds may be 

 expected then to expand or reduce the horizontal dis- 

 tribution of given river waters in the inner bay. Under 

 such conditions, one would expect it is largely Kvichak 

 River water (which occupies the northwest side of 

 Kvichak Bay) that is moved toward the east side of the 

 bay and that considerable mixing between Kvichak and 

 Naknek river waters would occur. The same situation 

 holds true for the other rivers entering the bay. Although 

 the horizontal distribution of individual river waters may 

 be expected to expand or be reduced under prolonged 

 strong winds, their seaward course should remain essen- 

 tially the same. 



SUMMARY 



Hydrographic studies were carried out in inner Bristol 

 Bay to determine the seaward course and distribution of 

 the waters of major sockeye-salmon-producing river sys- 

 tems draining into the bay. These studies were con- 

 ducted in conjunction with investigations of the early 

 marine life and distribution of adult sockeye salmon 

 while in Bristol Bay. They included: 1) determining the 

 vertical and horizontal distributions of salinity in the in- 

 ner bay; 2) tracking and plotting the distribution and 

 course of Naknek, Egegik, and Ugashik river waters dur- 

 ing flood and ebb with Rhodamine B dye; and 3) plot- 

 ting the seaward course of plastic drift cards released at 

 several locations in inner Bristol Bay. 



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