Rime And Its Importance To The Annual Water Supply by Wayne Browning - Biologist, Climate Researcher, NWS Observer On dark, cold winter days when cloud bases hang low across the great High Knob mass there is magic in the air. Literally! For when the clouds part, and sunshine returns, it is as if the Lord himself had taken a great brush and spread a blazing white blanket of sparkling crystals across the highcountry. Rime is thickest on the tallest trees.  Photo credit: Otis Ward. Residents of Wise, Scott, and Lee counties have looked upwards all their lives at the beautiful white trees which stand like polished jewels against the dark blue of a winter sky. Visitors are simply amazed. The substance which paints these gorgeous scenes is called rime, and while it may take different forms it is essentially frozen clouds of water! While rime may cap any of the taller mountains of the southern Appalachians, it is special on High Knob. For you see, High Knob is no ordinary mountain! Unlike most southern Appalachian mountains which rise to a peak, then drop off the other side, the crest of High Knob spreads outward for mile, after mile, after mile. When the High Knob Lookout Tower burned on Halloween of 2007 it broke my heart, like many others, but I was comforted by the fact that it is High Knob which made the Lookout so special to me and everyone who stood upon its grand ole form. High Knob is such a special landform because its sprawling mass contains unique places, like the great South Fork of the Powell River Gorge and high basin of the Big Cherry Lake. Much of which is owned by the town of Big Stone Gap. Many have recently been shocked by how fast the Big Cherry Lake returns to full capacity. Following the great water crisis of 2005, when the lake was drawn down to build the new dam, some predicted it might take years to refill the Big Cherry. I merely grinned. After 21 years of doing climate research on High Knob I write to you about something which has touched my very soul, and something which everyone needs to know. Rime on High Knob.  Photo Credit: Randall and Cindy Kilgore. Looking outward across miles of blazing white trees, coated with rime, generates an inner feeling that is hard to describe with mere words. There is amid such a humbling scene, a most powerful force that can be sensed in every way. It can be smelled, seen, touched, and even heard as the warming rays of sunshine begin dropping the rime off to the forest floor. More often than not, the forest floor on High Knob is snow covered beneath the white trees, and the snow collects the rime's frozen water. During a long period, such as occurred from January 13 through February 3 of this year, this riming process can happen multiple times as moist, northerly winds are lifted across the great High Knob landform (northerly winds are the most common rime former). Each time this happens the hidden, invisible water contained within the air magically appears as winds blow up through the trees to cross High Knob. If temperatures are below freezing, and solid objects like trees are present, the water vapor will freeze on contact and be captured. If the moisture laden winds blow across an area where there are no trees, this amazing substance called rime will never be seen and instead is carried across the mountain to merely evaporate away as the air sinks downward on the other side. Moisture is lost. Years ago this got my mind churning, and my heart skipping, as I began to realize how important this process could be to the water budget of a high elevation basin like the Big Cherry (the Big Cherry lies completely above 3000 feet). For you see there is more to the rapid refilling of Big Cherry Lake than merely rain! While much of Virginia has been sinking deeper into drought, and having wildfires, the Big Cherry was filling to the brim, with 12.50 inches of precipitation so far this year. By far the most in Virginia. The significance of that can simply not be over-stated. While a portion of that measured moisture fell as rain, a substantial amount fell in the form of snow. An important yet un-measured portion of the moisture which helped fill the Big Cherry was rime. Not measured since rain gauges typically do not collect rime. But trees do! Each time trees collect rime they eventually give it up to the forest below. When snow is lying on the ground the rime moisture becomes part of the snowpack. Every time rime forms and falls off the trees it adds more moisture to the snow, until eventually a high water content snowpack is created. Such was the case in January-early February of this year, as when temperatures warmed and rains came they combined with the high water content snowpack to cause a run-off so significant that it boosted the Big Cherry Lake by more than 16 vertical feet. Amazingly, this great rise occurred despite the massive leaking of the old water lines. When I hear that plans to log the water capturing wonder of the Big Cherry are going forward, even if it means limited logging, I stand in absolute disbelief since each tree is in this way an important water source! Given all the water problems of recent years, the climate trends that myself and other researchers around the world have documented in the past two decades, and the absolute priceless value of water across much of the United States, it is mind blowing that anyone would even consider decreasing the water quality and quantity of one of the nations most pristine supplies. That logging diminishes water quality is well established, but water quantity has been more debatable. It remains debatable in many places, but not in the Big Cherry. I have absolute proof of that, which anyone reading or hearing these words may also prove by merely looking up at the blazing white trees capping High Knob. When those trees are white, you know that the Big Cherry is collecting water! What I tell you now is the absolute truth, and any reader is free to go prove it. If one simply rakes all the rime collected off of a bush into a rain gauge, and melts it down, it will take very little math to realize how significant this process is given bushes collect only a tiny fraction of the rime of a large tree. If the bush is 5 feet tall, you will have to multiply your rain gauge melted amount by a factor of 15 to represent a 75 foot tall tree and by a factor of 20 to represent a 100 foot tall tree (but notice, since a bush is so thin and low to the ground they typically do not collect as much rime as big trees which stand tall in the swirling air, your estimate will likely be low). After you calculate that for one tree, you will then need to multiply your water value by tens of thousands of trees to just cover the ridges of the Big Cherry Basin. This amazing rime formation process has already occurred on 19 days during this mild winter. Last winter it occurred on 35 days, and during the 2005-06 winter it happened on nearly 50 days. That is like having a month or two of extra precipitation! If the Big Cherry were not so highly elevated, amid the rime zone, then this incredible process would not be a part of its water budget. But it is, and along with the natural enhancement of precipitation which occurs as air is lifted across the great High Knob massif, is a major reason why the Big Cherry fills so rapidly during the cold season. This area is so blessed to have the Big Cherry, surely all must admit. Layer of rime on tower pole on Eagle Knob.  Rime develops into the wind, so that in this case a northwest wind was blowing and the rime on the tower pole kept forming in layers and building upstream into the wind.  It can occasionally become very elongated under the right conditions.  Photo credit: Wayne Browning.   I belong to no environmental group. I have nothing against the Big Stone Gap town council or its general manager. I tell you this because its your right to know what I have discovered, and because this issue is much bigger than me or you. Please consider these important facts. Please let it be known, by unsigned letter, voice, email, or fax that for the good of tens of thousands across Wise, Scott, and Lee counties that you want the Big Cherry watershed to be protected from logging, to make certain this most precious water supply will remain pristine and abundant for future generations.