Spring Runoff Could Be Lower Than Expected Due To Extremely Warm February and March

Apr 4, 2017

Every year at the annual Spring Runoff Conference at Utah State University, Brian McInerny from the National Weather Service shares his predictions as to how snow in the mountains will turn into water for farmers and citizens to use throughout the summer.

J.KELSO: Brian has joined me here today in the studio, -  Thank you Brian -   so maybe you tell us more about the factors you have to consider to predict spring runoff ?

B. MCINERNY: I think a lot of people think that we have a certain percent of snow so that equates to a certain percent of runoff, and that’s not true, it’s how is the spring runoff going to be shaped by the spring weather.  If it’s cold and wet we get a much more efficient runoff, and if it’s warm and dry and we start melting prematurely then you lose a lot of it to evaporation, transpiration, the plant come back to life, the snowline gets away from the streams so it has a better chance of evaporating.  So the question is now what is the spring weather going to do after we have this very big snow pack of about 140 to 150% of median right now.

J.KELSO: And so far we have had a pretty warm February and March right?

B. MCINERNY: When you look at the data, when you look at the temperature warm up we were basically warm for February and March and we were up to 23 degrees above average for one of the days, and most days were up to 10 to 20 degrees above. And it looks like we are going to have the hottest March we have ever experienced, with this month now and these heat records just continue.

J.KELSO: So compared to the past and what’s predicted for the future, should we consider these warm temperatures to be extreme?

B. MCINERNY: The global average due to warming is 1.8 degrees averaged across the globe, Utah is warming faster than that, 2 to 3 times that rate, or 2 to 3 degrees I should say, so when you have increased warming what you get is earlier melting of snow packs and you get storms that used to be snow storms which are now rain events.  So when you look at all these things together we are going to get earlier melts, and we are going to get rain, and we are going to see storms with more intensity.

J.KELSO: And what do these increased temperatures mean for Utah’s snow pack in the coming decades?

B. MCINERNY: By about 2035-2065 we are going to see snow areas that are normally 100% snow pack in winter that are 50% snow pack or less, and that is going to impede how we do water.  We have this wonderful system right now where we have snow in the mountains, it stays there, it’s clean, it’s gravity fed, when we want it, it melts, it comes down channels that have been formed over thousands of years into reservoirs and then we dole the water out, it works really well and we do this year, after year, after year.  Well what happens when our snow hydrology, meaning we get snow in the mountains, starts to rain during the winter time, and when spring comes we don’t have the snow pack in the mountains, how are we going to provide water for Utah’s population, because roughly about 2100 we should be absent of snow in the Wasatch Mountains, it is going to be rain during the winter time.

J.KELSO: Wow, so this is a lot to take in for me because, you are talking about there being less and less snow, with warmer and warmer temperatures… but this year we have seen record snow pack that resulted in extreme floods in Northern Utah.  So with all this variability from year to year can scientists predict whether there will be more or less flooding in Utah?

B. MCINERNY: Let’s just take for instance the flood event we had here in Box-Elder or Cache county, you can say weather occurs and these events have happened before, you know 1874 is when we started climate records, its happened before and you could say its weather and your right, extreme cold, extreme heat, long term droughts, intense rain events,  big snow runoff  -  but it’s the trend that you need to look for in the data.  I think if you equate it to weight gain, you may think oh I’m doing okay but you are slowly getting heavier all the time, it’s not like this dramatic increase in weight, and then you look around and you think oh my clothes don’t fit so well, I got to get after this, it’s very similar to this, it’s a slow process but when you look at the record for 650,000 years  it’s an incredibly fast process. Within 30 years we have warmed to the degrees we are and then you look at the projections and we are expected to warm 12 degrees by 2100, and that’s frightening.