One of our goals is to get a sense of how much water leaves the glaciers and flows towards the ocean, and then use this information to better understand how much water glaciers in this region contribute to the major rivers of this region. But this is tricky business. ‘Normally’ stream discharge is measured by attaching instruments to the pier of a bridge or by pouring a lot of concrete to make a gaging station that wont be damaged by the force of the moving water and the rocks it carries. These are not options for us, so we have to find work-around solutions. In our case, it is much easier to measure the height of the water than the amount of water flowing. We do this by putting pressure transducers under the water and by suspending a distance measuring device above the water, and hoping that at least one of them will survive. Then we can come back periodically and manually measure how much water is flowing by wading across the stream and measuring water thickness and velocity with a handheld instrument. If we do this when the stream is at various heights, we can determine the relationship between the continuous height measurements and the manual water discharge measurements, so that we can then estimate discharge throughout the summer using only the automated measurements. Later in the summer we will then visit some of the larger rivers in the area that receive water from many different glaciers and make similar measurements there, and scale up our local measurements to estimate the overall glacier contribution.
So today we got a start on these measurements. Jason and Joey measured discharge at our natural wier (as opposed to a concrete one) formed where the river has cut through a moraine formed by the glacier about 30 years ago. We then suspended a cable across the river to hand our distance measurement device on. Jason also set up a pole on the river bank that will hopefully be photographed by our time-lapse cameras, such that as the river rises and falls it will obscure more or less of the pole and give us a back up to the other instruments. The precipitation didn’t let up until dinner time, and I think this was about the coldest we felt on the entire trip, even during the April storms. The cold, humid weather combined with a slight breeze from the terminus is bone-chilling, especially when you are up to your knees in ice cold water.
The stream was still low compared to peak summer, but cold and fast nonetheless.
Jason wades the stream and uses the headset on the radio to relay the measurements back to Joey, who records them in the field book.
Jason: “Welcome to McCall Creek, can I take your order?”
Unlike yesterday, Turner spent most of the day in the tent. He does an amazingly good job navigating the rocky terrain for a two year old, though I don’t have much basis for comparisons. Just when you think he’s about to miss a step and faceplant into a boulder, he plants his foot and hops to the next rock. It’s a little nerve wracking, and the many bumps and bruises on his legs and arms indicate that he doesn’t always succeed with his plans, but he’s never more than a few steps from us and so far his skills and judgment continue to improve. Having backpacked down here, we don’t have a lot of toys for him to play with, but his creativity seems to make up for that. Jason gave him a river rock on our first night here which is now his ‘dinosaur egg’, which he keeps warm and hatches about 60 times an hour. We also play swords with survey stakes, play jump over the instrument cables, chase the ‘rats’ (more rocks), and other invented activities. But today it was more fun to hatch the egg in the tent, out of the rain and snow and wind, and that seemed reasonable enough. So far tonight is dry and calm, so hopefully our hike back tomorrow will be pleasant and he can walk and ski on the ‘big ice’ and play with his other toys tomorrow night in ‘other home’.
It’s Dumbo’s turn to hatch the dinosaur egg.