Earth & Sky

Interview with Gordon Grant.

ES: Thanks for speaking with me today. Could you give me some background about the hydrological buffer in Western Oregon?

GG: The hydrological buffer issue emerges when comparing what we’re doing here in Oregon with what we think would happen if you did this same work in California. So what I’m going to do is talk about the work that I’m going to do in Oregon and work my around to that issue.

As you may know, it rains a lot in Oregon. But most of that rain comes in the winter. The summer is very dry here. And yet, if we were to go out into the river in late September, after there’s been maybe three or four months of dry weather, you would still see water, some quantity, flowing down out of the mountains. The mountains I’m talking about specifically are the Cascade Range of Oregon, the western slopes of the Cascades. And this is known well by people in this state. But the reason for it isn’t clear. If you ask the average person on the street, well why does the river still have water in it when it hasn’t rained in four months? Most people will give you one of two answers. Well, it’s snowmelt. It’s slowly working its way down to these larger rivers. Or, it’s the dams. And there also are flood control dams that release water into the summer. Both of those answers would be partly true. That is, there is some late season snowmelt, and the dams do have some role in augmenting flow. But, the reason why there’s water in rivers draining the western slopes of the cascades, such as the McKenzie in late summer, is because the central region of the state, the Cascade mountains of Oregon, are in essence, a vast hydrological sponge. And they’re a hydrological sponge, in the sense that they are a recent arc of young volcanoes, including young volcanoes that erupted as recently – not in Oregon, but in Washington, St. Helen’s erupted in 1980 – 20 some odd years ago. In the central portion of the Cascades of Oregon are vast volcanic fields with lava that was erupted, in some cases, 1500-3000-6000 years ago – very, very recently in geological time. If you stand on this lava, or if you walk around on them, first – you can barely walk. Because, what you’re walking on are these blocky, chunky, large fields of lava that still retain almost all of the structures of where it cooled. That is, it is literally frozen lava more or less where it came out of the ground. Now, when they train people to walk on the moon, they actually did so in central Oregon, just to give them the experience of walking on this rubbly, blocky surface. Because the lava is so blocky, they’re incredibly permeable. You could bring a fire truck to the top of the Cascade Mountains, and run water all summer long over the ground, and you’d never see it run off the ground. It would all go down into the sub-surface. And so, in a very real sense, the central zone of these young, volcanic mountains is acting like a sponge – it’s literally soaking up the winter precipitation and releasing this water over time, typically as springs that emerge many thousands of feet lower, and in many cases miles away. And it’s that water, that deep ground water that’s percolating first vertically, through these lava fields, and then moving horizontally out of the high cascades and emerging as springs. That is the major reason why there is water in the river in the late season. And so our research has really been to focus on understanding this rather complex plumbing system. And it’s complex because it’s not at the surface. You can’t trace where a raindrop or a melted snowflake, you cannot trace the path that that follows as it moves through the landscape. But where you first pick it up, it’s emerging, the water is emerging, as these voluminous springs, entire rivers literally just appear out of the ground. And so our research has been to ask some very basic questions about where this water is coming from. We’re asking questions such as, how old is the water? When did it come out of the sky? How much of a reservoir is there? How much water can the sponge hold, if you will? How variable is the water? Is it full of water. Does it vary from month to month, from year to year, and from decade to decade? How cold is the water? And this is the source of cold water that is the source of our aquatic species, including our endangered species need to survive. And so we’re using a variety of different clues, and a variety of different techniques to answer these questions.

ES:

GG: No one really discovers something of this magnitude on their own. In fact, the idea that the young volcanic terrain of Oregon is the source of the springs that one finds on both sides of the Cascades has been known for years. And the first geologists in this area commented about the very large springs that one could find here. But the extant to which this groundwater system dominates the flow regime of, particularly late summer flows, is relatively new – in the sense that the importance of this, I think, has not been fully understood. And, the reason we got on to this story is actually from work that we’ve been doing on the other side of the mountains. The Cascades are a north-south trending range that sit up in the path of the prevailing moisture which is coming in off the ocean. So there’s upwards of ten, and some cases fifteen feet of water that come down every year into the Cascades over the course of the winter. In central Oregon, that water drains on both sides of the mountain, with most of it flowing to the west, because that’s where the major source of water, and this is the way that the westerlies bring them in. The eastern side of the cascades is much drier. But nonetheless, the water that falls on the cascades makes its way out as ground water and emerges also as springs and feeds some very large rivers, or at least one very large river, the Deschutes river, on the east side of the main crest. It was our work on this river that really got us thinking about how the cascades are working. Because we discovered that the Deschutes river is one of the more unusual rivers, I would argue, on the face of the earth. So, the rivers are peculiar because they’re fed by this very big groundwater system, this deep groundwater system. We decided – the work that we did on the east side made us think that this same story must apply on the west side. But the spring systems, and the extent of the groundwater influence was much less clearly understood, in part because the landscape is densely vegetated, they’re dense forests. Much of the high country is an wilderness area, and many of the springs have not even been found, many of the large springs. They’re not even on the maps. And so our work was an effort to capture the extent to which the rivers draining the west slope of the cascades also had this same pattern – this pattern of having very stable stream flows, very cold water, and very constant flows, even under conditions of where there has not been rain for extended periods of time. And we discovered that there was a range in the extent to which different rivers express this, with the McKenzie river being the poster child for this kind of spring-dominated river system.

ES: So what was some of the work you did in studying the McKenzie?

GG: Well, initially, we have gone out just to identify where the water’s coming from. I mean, in some cases, the methods were no more elaborate than just finding springs that were known only to a few people within the Forest Service. And where we discovered springs – and identified springs that others had already found – we set up to measure the flow of water coming out of the ground. The springs themselves had never been adequately measured at all in terms of their stream flow. So we installed permanent stream-flow measuring sites. We installed permanent and continuous measurements of temperature, and the temperature turns out to be a pretty useful way of understanding where the water is coming from, because the temperature of the water and the issues from the springs is extraordinarily constant. We have springs that vary no more than a tenth or two of a degree over the entire course of the year. Water is very, very cold – it may be no more than 4 degrees to 5 degrees centigrade. That’s like 38-42 deg Fahrenheit. And these springs themselves have very constant stream flow, but there’s subtle variation over the course of the year. So we set up to measure these things. Additional set of measurements that we did was to collect stream water with which to conduct isotope chemistry. And, another clue to where this water is coming from is to look at the concentration of heavy isotopes of oxygen in the spring water, and to compare that with known calibration curves for oxygen 18 in precipitation. Without getting to technical, the amount of heavy oxygen which naturally occurs in rainwater varies as a function of elevation, with less heavy oxygen occurring at higher elevations. Basically the heavy oxygen falls out first. So you can relate the concentration of this isotope in the spring water, to the average elevation that’s feeding the spring. So even though you can’t see where the water is coming from, directly, you can use the isotopes as a kind of tool to estimate what the recharge area of the spring is.

ES: Where does all this water come from and go to?

GG: So, in the mountains of Oregon, water falls from the sky, and it falls out in different forms – it falls out as rain, and it falls at higher elevations as snow. And, once the water’s on the ground, it can follow different paths to get to the river. Some of the water falls off directly and falls into the streams falls into shallow soil and runs directly into the channel. Other portions of that water that falls out as snow is actually stored on the landscape as a snow pack, possibly in glaciers, and then will melt during the spring season, and then runoff directly into the stream, or move down through the subsurface. So, you can think of, the water that’s falling out of the sky as following different flow paths. Some of its stored on the land surface as snow and then either a surface or subsurface flow path. But then all of it eventually, and some of it going directly and deeply into the groundwater. So, the water that’s in the river at any given time is some mix of these different pathways by which water has reached it. It’s a mix of rainwater, it’s a mix of snowmelt, and it’s a mix of deeper groundwater. At different times of the year, different pathways will dominate in feeding the river. So for example, the recipe for a flood in western Oregon is to have a deep mountain snow pack – that is, lots of water stored as snow on the slopes of the mountains – and then bring in a warm rain with warm winds that rapidly melt that snow pack. Then, all of a sudden you have both rain and snowmelt combined. And there’s more water available than can be absorbed into the ground – that can infiltrate into the ground – and most of that water then runs off directly into the rivers, and we get a flood. That’s the recipe for a flood. And under those circumstances, we would say the flow regime is dominated by rain and snow, typically rain on snow. During some periods of the year, though, there is no rain, and there’s very little snowmelt, so that the flow regime – that is the amount of water, and the volume of water, and the fluctuation of water within the channel – is resulting entirely from the pattern of the groundwater. And in that case, we would say that the flow regime is being dominated by groundwater.

ES: So one of the things you and your co-researchers found is that the Deschutes is flowing steadily because of the deep groundwater?

GG: Right that’s what we discovered. And, this has been known for the first people out there, the first people to scientifically study these rivers in Oregon noted that the Deschutes river had the most stable flow regime for its size, of any river in the country. And, what that means is the difference between high flow on a river like the Deschutes, and low-flow, can be no more than a factor of four or five. High flow may be only a factor of five times what the low flow is. In most rivers, the difference between high flow and low flow is a factor of 20, 50, 100, or more. That is, rivers flood in the winter, and they’re very low in the summer, at least around here. So, stability of the flow regime is one indication of where the water is coming from. And the Deschutes is remarkable in its constancy of flow.

What is emerging from this work in the Cascades is that the water that is in the river today may have fallen out of the sky two, five, ten, or even longer years ago. Because it’s working its way into this deep, groundwater system, the water that’s actually in the river today can be years, or even decades in age. Of course it’s mixing with water that may have fallen out of the sky last week. But, the mean age, the average age of that water, we think from work that others have done on the east side, suggests that the mean age of the water may be from five to ten years old. What this is pointing in the direction of is there is a large volume of water that is stored as groundwater, as deep groundwater – the sponge. And so, every year, more water is added to the sponge in the winter, and every year some water comes out of the sponge during the summer. But the sponge retains a substantial volume of water. And, how much water is still a mystery. But we believe it’s substantial. What this means now is that if we get a year, or two, or maybe three – if we get a period of dry weather that may last for several years – the streams that are draining this hydrologic sponge are likely to show much less variation. They’re not likely to run dry to the same extant of streams that don’t have this hydrologic sponge as their primary source of water. What we think this means is that – in the coming years the climate will change, whether it’s changing because of anthropogenic, or human causes, or natural variation, what we know about climate is that it will change – but in the case where river systems are sourced by these deep groundwater systems, the sensitivity of the flow of the rivers to change, and we also think the sensitivity of the temperature regimes to change is substantially less. Compare this if you will to a landscape like the Sierra mountains, the Sierra Nevada in California. The Sierras have a very different geology than the cascades in Oregon. The Sierras are a large, granitic complex that’s been stripped and eroded, primarily by glaciers. The Sierras lack this hydrologic sponge. Water that falls during the year also can be stored as snow, or it can directly run off, but very little of it enters the deep groundwater flow path. Because of this, the flow regimes of the rivers of California are much more sensitive to year to year variations in climate. There isn’t that deep reservoir, there isn’t that deep volume of additional water that can, in a sense, buffer the effects of variation in climate. And so, in the future, as climates change, it is likely that the rivers draining the rivers of California will be more sensitive to the fluctuations that climate change imposes than rivers that are fed by these deep groundwater systems coming out of these volcanic terrains in Oregon. And this has implications for water supply, for where cities get their drinking water, from where the aquatic ecosystems get the water that they need to sustain themselves.

ES: What are some of the issues surrounding how the Deschutes is managed?

GG: Water is increasingly being seen as one of the most important and potentially scarcest resources into the future. And the prospect that of changing climates – either due to natural or anthropogenic causes – only heightens the importance of water as a resource, and it heightens the importance of understanding where the water comes from. Because people need water, fish need water, river ecosystems need water, industries need water, farmers need water – water is front and center in our thinking about what future resource consumption patterns will be. We’re already seeing the issue of water emerging as a conflict in basins like the Klamath river, where issues like, during a dry year there may not be enough water to go around to maintain both an agricultural economic base and an aquatic ecosystem. Decisions about how much water will each group or each resource get are increasingly making their way onto the front pages of the newspaper. And so, resolving these issues are going to involve where the water comes from, how much water there is, and how sensitive the water resources are to the fluctuations in the climate. So, this template, this geological template, of whether the natural system, the natural plumbing system if you will, provides for a continuous, constant flows of water, or is much more dominated by episodic and rapid fluctuations in the amount of water that comes down the river is of critical concern to people who have to make decisions about water allocation, and water consumption.

ES: How has research into the origin and quality of river systems like the Deschutes affected policymakers?

GG: I’ll tell you, it hasn’t really made its way into the policy arena yet. I mean, if you’re looking for – this is right where we are right now. In other words, what’s happening is that the conflicts over water are really pushing the question of where is this water coming from, what quality is it, how much of it is there, right into the forefront, right into the arena where we’re having to make decisions about who gets how much water. In general, we know where water is coming from. We have a very extensive gauge network of stations on streams that give us a reasonably good picture of where water is coming from. We know that this river has more water in it than that river on a seasonal year-to-year basis. What we don’t know, and where this research I think is really pointing us, is whether entire regions that are having to make these decisions and choices between various ways that water can be allocated. We don’t really understand the extant to which the basic geological template in large measure determines whether or not different regions are likely to be more or less sensitive to water shortages down the road.

ES: So tell me a little about how the ecosystem is connected to this river system – how stressed is it?

GG: The research we’re doing, I think, is providing a kind of roadmap for how to think about the sources of water and particularly the sources of water of different temperatures, and how that might change under different climates. The key issue is that aquatic ecosystems tend to be very sensitive to differences in water temperature. So we have species such as the bull trout, which are really adapted to cold water. And if you find bull trout in your river, then springs probably can’t be too far off. Because the fish are adapted to a particular, constant cold temperature. If, under different climates, under a dry season or a dry year, the proportion of water – coming from either ground water or surface water – is likely to change. And that’s likely to have impacts on ecosystems, but in ways that we don’t fully understand, in part because we haven’t really used the geological template as the basis for understanding variation in geologic ecosystems, at least to any substantial degree. We’re just beginning to use this understanding of how the geology, in a sense, structures the pattern of ecosystems that we see, and their likely sensitivity to environmental change.

ES: What kind of future do you predict for the Deschutes?

GG: Well, it’s the typical science weasel to say that, “well, we really don’t understand,” but truth is, we really don’t understand. What we’re beginning to learn is that the river that you stand by today is a mix of water coming from different sources – it follows different pathways. Those pathways are going to have different degrees of sensitivity to environmental change. Spring fed streams, for example, we would expect to be relatively resilient, at least in the short term, to a period, say of drought, or even extended periods of wet. And we can’t predict how the future is going to be. The climate models generally suggest, at least on the West Coast of the United States, the winters will be warmer and wetter, and the summers will be hotter and drier. What that’s going to do, if that comes to pass, is accentuate the differences between springs that are dominated by spring water and streams that are dominated by surface water. Because, what it will mean is, if we can imagine a future where summers are hotter and drier, and winters are warmer and wetter, in which case the snow packs which might have persisted into June, under the current climate, might be melting off in April or May, under some projected future climate. Under those conditions, the difference in late season water will be most pronounced between springs that are dominated by springs, spring-fed sources, and those that are dominated by surface water sources. Basically, the streams that are sourced by surface water, unless they are fed by glaciers or really large snow packs, have a much higher probability of running dry in the late season, in the Mediterranean climate of the West Coast. So, in that case, we might anticipate that ecosystems that are currently keyed into those sorts of rivers are going to be under additional pressure.

[something about dams]

ES: Okay, going to switch gears a bit and ask you talk a little about the research you’ve done on dams and dam removal.

GG: Dams play off the story that I’ve been giving you, in that dams are the way that we store water during periods when water is plentiful – in the west coast, that’s the winter, and release it during times when it is scarce – in the west coast, that’s the summer. In a sense, the groundwater system that I’ve been describing functions as a vast diffused dam, if you will. That is, it functions in the sense of – it stores water during the winter, and it releases it slowly during the summer. So in a sense, in the case of the Cascades of Oregon, you can think of them as sort of a tremendous, natural dam and reservoir. In the absence of natural reservoirs, people have constructed dams and reservoirs. In the future, if the climate scenarios that the models are suggestion – and we have to remember that they’re just models – they tend to paint a fairly consistent picture from one model to the next, which gives you at least some confidence that there is a story there -if the story that the models are painting is the direction that emerges in the future – that of warmer, wetter winters, and hotter, drier summers – what that’s likely to mean is that the dams will play an increasingly important role in those portions of the landscape that don’t have other ways of storing water in the west coast. So in the Sierras, for example, where there is no deep groundwater system. The only storage in the land is either in the snow pack, or in the reservoir. If the snow pack melts out early, then that just leaves the dams. So, this is a projection, but one can anticipate in the future that the needs of cities, and of agriculture, and of ecosystems, are all going to be ever more, increasingly bound up with how we manage dams and reservoirs.

Well, let me just warn you that this is a whole other Pandora’s box. I mean I’m happy to talk about it – I give lots of talks about dams and dam removal. But, in my mind at least, I try and keep these stories somewhat distinct, not because they’re not related, but because they’re both complicated stories with their own twists. And you can really befuddle people if you put too much on the plate ate once. But with that as a caveat, let me talk a little bit about dams and what’s going on.

We have a lot of dams in this country. Depending on who you listen to, numbers of 75,000 or 100,000 or more, depending on what you consider to be a dam, are thrown around. Most of those dams are small dams. That is they’re 10-15-20 feet high and maybe equally wide. Most of them were built during the middle part of the last century, that is in the 40s and 50s and 60s was really the height of the dam-building period. And what that means is that a lot of them are getting older. They’re approaching their design lives, which were on the order of 50-100 years. And, so decisions have to be made about what do we do with them. Left to their own devices dams as they age, they degrade, they begin to pose safety hazards – possible dam failure and leakage. And the question is emerging, what do we do with this aging infrastructure of dams. So, increasingly, people are asking themselves – do we need these dams, particularly the ones that are old and may have outlived their usefulness. And, again I want to emphasize that most of these dams are very small. At the same time, there is an ever-expanding set of objectives for rivers. When many of these dams were built, ecosystem issues were not particularly well understood and were not particularly current in terms of the objectives for what these dams were constructed. They were constructed to capture water, to provide flood control, to reduce sediment loads downstream, to provide for irrigation. And many of these objectives are still with us, but at the same time, there are additional objectives. We want our rivers to provide for healthy aquatic ecosystems, we want them to provide for recreation. So the palette of issues, and the palette and the palette of expectations for our rivers has changed over time. And so that’s the backdrop against which this discussion about whether we need, how to think about our current infrastructure of dams. Clearly there are dams that are providing many positive benefits and are likely to be retained or reengineered in the future to meet this expanding set of expectations. Other dams may be full of sediment, may be posing safety hazards, maybe in danger of removing themselves – and in that case there is increasing interest, in deliberately and proactively going in and taking these dams off the river with a potential attendant benefits of providing fish passage into perhaps parts of the river where these dams presented a barrier. At the same time, removing these dams poses a set of problems in and of itself. In that removal of a dam may release pulses of sediment into the downstream river, which may cause a set of ecosystem and physical changes to the river. There may be contaminants stored behind some of these dams. So, it’s a tricky business to try and figure out which dams can be removed, how to remove them, and whether it’s worth removing them. And really, it’s at the point – this is where the discussion is at this point. We’re trying to bring the scientific basis to help us understand how these dams are behaving, what’s likely to happen if you take them out, what the environmental benefits and costs will be if you take them out, and help decision makers make intelligent choices about which dams should stay and which dams should go.

ES: Let’s go back a bit and talk about the rivers themselves, perhaps you can describe to me a little more fully the character of the Willamette river system.

GG: So, our research has been concentrated in the Willamette river basin, and especially the McKenzie river, which is a major tributary in the Willamette in western Oregon. So the McKenzie flows out of the Cascade mountains, which are a north-south trending range of big volcanoes – Mt. St. Helens, Mt. Hood, Mt. Jefferson, and so forth. And, the McKenzie comes out of the central portion of the Cascades, and flows westward through an older volcanic landscape, which is the older Cascades, or Western Cascades, and eventually turns north and joins several other tributaries to become the Willamette river, and the Willamette then flows north through the Willamette valley, the most populous portion of Oregon. I think 85% of the population lives within 15 miles of the river. Eventually, the Willamette empties into the Columbia at Portland, Oregon’s largest city. So, the McKenzie starts at the high Cascades, the volcanoes there have elevations of 10, 11 thousand feet. And, it’s fed, but most of the water is coming from the broad uplands of the Cascades, and from the western Cascades which is the area that it flows through as it goes to the west.

So, the McKenzie’s been a river for the last three or four million years, but, it’s taken a series of geological hits over the last million years. The river – because it’s draining in an area of active volcanism, periodically volcanoes emerge, erupt in its headwaters sending ash and hot pyroclastic flows down the upper reaches. Over the same time scale that that’s occurred, and volcanism’s occurred throughout the last million years, but there’s been quite a bit of it throughout the last 10,000 years. Over those same time scales, there have been major episodes of glaciation within the cascades, so major ice sheets have come down out of Canada. Large icecap glaciation has blanketed all of the upper elevations, and the tongues of these glaciers have flowed down the major rivers. So the upper McKenzie shows both its volcanic history, which it tends to build it up, and its glacial history, which tends to erode it down. So you can see the river resulting from these two major landscape altering forces duking it out – volcanism and glaciation.

ES: What are some of the forces that continue to shape the river?

GG: The forces that shape the river continue. There’s current suggestion that a low bulge is emerging in an area that has seen fairly recent volcanism within the Three Sisters Wilderness Area, and it’s possible that we might have another volcanic eruption sometime in the decades to come. At the same time, land use patterns within the river changes in the ways that both private and public lands are managed for forestry are changing the vegetation within the watersheds, are changing patterns of erosion within the watersheds, are changing expectations for rivers, are also changing the channels. So, for example, the (Army) Core of Engineers is currently retrofitting one of the large flood control dams on the McKenzie to allow it to provide better temperature controls and better temperatures for aquatic ecosystems. That’s changing the river. Population is changing the river. The communities that, in the case of the McKenzie, the Eugene-Springfield area is growing, and the concurrent demands for water as a population increases. Agricultural demands are changing. People are changing patterns of what they’re growing – that also changes the demands on the river. Recreation is changing the river. Thirty years ago, there wasn’t much of a white water boating industry. Now it’s sprung up on the McKenzie. So all of these different human and geologic scale processes are occurring more or less simultaneously. And they’re all having an effect.

In the case of the McKenzie, the work that others have done suggests that the McKenzie may be one of the more resilient rivers in the face of increasing population demand, in large part because of this relative stability of its stream flow regime. That because it’s fed by a large groundwater system, there’s still quite a bit of water in the system even in times when other rivers have run dry. So, what I think that will mean is that there will be increased pressure on the McKenzie. It will be the only game in town if there is a period of extended drought. So this raises all kind of issues about how do we manage a river so that to recognize that there will be times of scarcity as well as times of plenty?

Useful web links:

Nice Map here at West Multnomah Soil & Water Conservation District’s web site

The following person was interviewed for today’s program. Our thanks to:

Gordon Grant
Research Hydrologist
Pacific Northwest Research Station
U.S. Forest Service