A couple of additional thoughts on drought
These are not necessarily past of last night's forum, and i didn't know how to incorporate them into the post below.
First, a lot of people, myself included, have been commenting on how the reservoirs in Durham are now full. We're not necessarily drawing the same conclusions from this, however. I'm not convinced that the drought is over, for instance, although i do believe that the crisis mode we were in last December has passed, and i'm comfrotable with the current Stage III restrictions, at least for the time being.
But, not counting whatever rainfall we get today, we're still 1.9" below normal rainfall for 2008 so far, and we're a full 5.8" below normal for the past 12 months. But even with this shortfall, we've managed to top off our reservoirs. The logical conclusion from that is not that the drought is over. Rather, it's that we have very small reservoirs. And if they filled up that quickly, they can be drawn down that quickly.
The second thought has to do with conservation measures alluded to below. I'm not referring solely to retail conservation at the consumer level. We don't have to declare a moratorium on development, for example, to institute workable conservation policies at the development level. One thing that i finally realized last night is the relationship between runoff and ground water. Most suburban type development entails creating a lot of impervious surface. Why is impervious surface bad? Because it increases runoff.
But runoff goes to the streams, and the streams go to the reservoirs, and they get filled. So what's the problem.
Well, the reservoirs are already filled. So all that runoff is, so to speak, water over the dam. Not to mention all of the pollution and unwanted nutrients that get carried directly into the streams and rivers.
We've got two places to store water - the reservoirs and the ground. Think of them as bowls and sponges. We can only make our bowls so big. Once they're filled, that's it. And it's expensive, not only in terms of cash, to build more bowls. But the sponges take up most of the area around us. They soak up and hold a lot more water, releasing it more slowly than runoff, and helping to keep the water flowing into the bowls even when the rainfall is less than adequate. All the impervious surfaces we build make the sponges smaller, without increasing the amount of water we can hold in the bowls. So, it shouldn't be too difficult, as a matter of policy, to tie development practices to making sure the least amount of impervious surface per project is created, and the more sponge is left to help keep the groundwater where it belongs.
First, a lot of people, myself included, have been commenting on how the reservoirs in Durham are now full. We're not necessarily drawing the same conclusions from this, however. I'm not convinced that the drought is over, for instance, although i do believe that the crisis mode we were in last December has passed, and i'm comfrotable with the current Stage III restrictions, at least for the time being.
But, not counting whatever rainfall we get today, we're still 1.9" below normal rainfall for 2008 so far, and we're a full 5.8" below normal for the past 12 months. But even with this shortfall, we've managed to top off our reservoirs. The logical conclusion from that is not that the drought is over. Rather, it's that we have very small reservoirs. And if they filled up that quickly, they can be drawn down that quickly.
The second thought has to do with conservation measures alluded to below. I'm not referring solely to retail conservation at the consumer level. We don't have to declare a moratorium on development, for example, to institute workable conservation policies at the development level. One thing that i finally realized last night is the relationship between runoff and ground water. Most suburban type development entails creating a lot of impervious surface. Why is impervious surface bad? Because it increases runoff.
But runoff goes to the streams, and the streams go to the reservoirs, and they get filled. So what's the problem.
Well, the reservoirs are already filled. So all that runoff is, so to speak, water over the dam. Not to mention all of the pollution and unwanted nutrients that get carried directly into the streams and rivers.
We've got two places to store water - the reservoirs and the ground. Think of them as bowls and sponges. We can only make our bowls so big. Once they're filled, that's it. And it's expensive, not only in terms of cash, to build more bowls. But the sponges take up most of the area around us. They soak up and hold a lot more water, releasing it more slowly than runoff, and helping to keep the water flowing into the bowls even when the rainfall is less than adequate. All the impervious surfaces we build make the sponges smaller, without increasing the amount of water we can hold in the bowls. So, it shouldn't be too difficult, as a matter of policy, to tie development practices to making sure the least amount of impervious surface per project is created, and the more sponge is left to help keep the groundwater where it belongs.
Labels: drought
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1 Comments:
We've got two places to store water - the reservoirs and the ground. Think of them as bowls and sponges.
I prefer to think of them as a series of tubes.
I like this chart for keeping track of rainfall. A lot of people think the problem is that we're not getting enough rain, but that's something of a red herring. We're down by ~15% from normal, but lots of places get by on way less total rainfall than even our drought numbers.
The real problem is that our infrastructure just isn't up to the task, and that's largely because historically we haven't had to care. Hopefully this will be a wake up call to improve the storage infrastructure.
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JeremyT, at 10:02 AM
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