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r ~, I c:;- It v~, ,; ': :J eration and navigation throughout the normal eight- month season. Basically, for a flood control action, we store water during the peak runoff periods and evacuate it during the late summer and fall when there is a lesser chance of !load problems downstream. Hydroelectric power. All of the dams have power units. There are a total of 36 in all. Almost all of the water that is released from the reservoirs is used to generate hydroelectric power. The exception is down at Gavins Point where we have a somewhat limited discharge capacity. This is a typical day back in 1983 when power was generated at low rates during the evening hours or early morning hours and muc.h higher rates during the day. I show this because it shows that Big Bend, because it is situated in the headwaters of Fort Randall, can be shut off at night and used only during the day when the peak powers are the highest (when the power demands are the greatest). The system reached normal operating levels for the first time in 1967. That's the first red bar that is shown on that graph. It shows that we've generated about 10 billion kilowatt hours of energy on the average since the system filled. Some big runoff years were higber than that. 1987 was only 9 billion kilowatt hours. That power is used to great advantage, provided at a very cheap cost to its customers and serves a great number of customers. That's approximately the amount of en- ergy needed to support both of the states of North and South Dakota or the state of Nebraska. It's marketed in the Dakotas, Montana, Minnesota, some in Iowa, some in NebTaska. [ should have mentioned in talking about hydro- power that this rule book, this master manual we have, also describes how much support we give to hydro- power. Basically, navigation drives the wagon during the eight month navigation season. But we do things within the system to try to meet the wintertime power demand as well-like draw down Fort Randall reser- voir to a lower than normal level and refill it during the winter months so we can generate power with the water that can be released from both Oahe and Big Bend. We also transfer some water from Fort Peck down to Garrison and Garrison down to Oahe in order to increase the winter energy generation. Now we will talk a little bit about navigation. I had my first opportunity to ride a commercial tow this summer and I really enjoyed that. This river is a rather narrow one, and as you've been told it has no locks and dams. It's simply an open, !lowing channel. There is a great deal of skill involved in navigating with a tow on this particular river because of the currents. I was in a tow that had a total of six barges in it and that boat captain was really working to keep the tow where he wanted it. The navigation channel extends from Sioux City down to St. Louis, 732 miles in total. A six barge tow like the one I happened to be on has a capacity or equivalent storage of 75 jumbo hopper train cars or 300 semi trucks, each hauling 875 bush. els-a lot of grain. Most of the materials shipped on the river are ag- ricultural products. The amount of shipment is rather disappointing. About:> million tons a year. The thing I want to point out with this chart (Figure 4) is that in the earlier years we had most of the shipments downstream, that's the brown bars. The upstream bars reflect the amount of material being brought into the river. Notice the more equal balance between the up- stream and downstream shipments. It was mentioned that our designed channel is 300 feet wide by nine feet deep. We schedule our releases to meet certain !low targets that are designed to give that channel dimension or to maintain t.hat channel dimension. Generally it is exceeded, but there is a !low rate of 31,000 cfs at Sioux City and Omaha, 37,000 at Nebraska City, and 41,000 at Kansas Cit.y. I don't. ex- pect that you wiII remember those numbers, and they probably don't mean much, but I wanted to point out that we release as much water from the system as necessary to maintain those !low targets. That is, if we have an adequate water supply. I hope this drawing will demonstrate how we actually schedule releases in support of navigation. If we have a full system, if we are operating up in this annual !load control zone or the top part of the carryover zone, we provide what we call full service. That is, meeting those navigation targets that we just looked at for a full eight- month navigation season. If, however, a drought worsens and we dip deeper into this carryover storage, we provide something less than that. We wiII reduce those target !lows by as much as 6,000 cfs in order to conserve water in the system, still meeting an eight month nav- igational season. If we are in a drought, like the drought of the 1930s, where it is very severe and we are losing stored water, there is a point in the mul- tipurpose carryover storage where we actually reduce navigation to less than eight months. We would pro- vide no less than that minimum service that I speci- fied, 6,000 less than the full service, but we would reduce releases earlier in the season and provide some- thing less than an eight-month season. The master manual that we referred to tells us at what points we ought to start doing that. 29