Can rock dams reverse climate change?

the chirikawa mountains are a land of history wilderness and wonder in southeastern arizona but like many places these mountains have been subject to intense pressure from westward expansion climate change and unsustainable land use practices however there is one watershed in the chirokawas that is deviating from this trend and showing evidence of remarkable restoration potential a place where natural infrastructure in dry land streams are supporting adaptation to and protection from climate-related disturbances and stressors this is turkey creek situated on the el coronado ranch and it is an oasis in the chera cows maintaining water where it

had been lost over time using nature-based solutions managed by josiah austin and valaire austin clark from 1982 to 2022 its story has intrigued scientists for decades i remember the first time that i came here was in february 2013 with a large group of people and we came through and we were all amazed at the land management that the austins had done here where they had created these ponds and swimming pools and bathtubs all up and down the forest lanes where they were harvesting water and i could only think that the feeling that i got looking

at these structures was completely indescribable because it was so powerful the amount of earth that was being moved and the amount of water that was being harvested and it was also indescribable related to my professional career because there was no metrics and there was no scientific quantification that described the mechanisms that were happening in the hydrology here and that made me really excited about creating an experimental laboratory the extraordinary thing about this watershed is the sheer number of rock detention structures the austin's installed dr norman and her team were able to capture gps data on

over 2 000 structures and remarkably that may be only a fraction of the total so my husband started building small rock dams to to harvest the water and to control erosion and where he did that we noticed that the grasses came in and they stayed green during the dry season and when i say a few dams he built several thousand we were very lucky where we started putting these loose rock structures here at el coronado you know i put in one or two to protect a road after we put it in that area i noticed

that the grass was greener on both sides of this it was almost like a retention wall and i thought well if it works here you know let's put in a few more of them so i put in a few more and i got instant results you know after 20 years we have 20 000 of these loose rock structures if somebody had come to me and said you know joe austin what you need to do is put in 20 000 loose rock structures i would say you're crazy there is no other watershed in the united states

that boasts this sheer number of structures making it the perfect location to conduct studies on their impacts and by comparing the data collected from an adjacent watershed rock creek where there are no check dams installed the usgs was able to establish a paired watershed experiment to draw and compare quantifiable insights about how the water behaves and how the land responds in the presence and absence of rock detention structures using existing weather gauges to monitor rainfall or the input of water into the watersheds the usgs established modified continuous slope area gauges in both streams to capture

high resolution data on how high the water rose and how fast it receded after a rain event continuously recording pressure transducers crest stage gauges and direct measurements of streamflow were used to develop stage discharge relationships while gps surveys terrestrial lidar and three-dimensional models refined their knowledge of water yield and sediment loads over time additionally soils were sampled to analyze their organic material using isotope analysis now i'm standing in the turkey pen sub watershed uh this is uh one of the tributaries of the turkey creek that we were just looking at and this is one of

the areas that the austins had invested a lot of effort into slowing the water down you can see here these are small rock check dams that they put into this watershed the water here is running pretty slowly if you look down you can see it's also very clear so they're not very tall but they stretch across the width of the channel we don't see much incision here and very little exposed bedrock now we're standing over in rock creek this is the watershed that's just adjacent to the turkey pen watershed you can see the water flowing

here is flowing a little bit faster and it is flowing over rock there's a lot of exposed bedrock here the water flows through deep channels with large boulders and it flows much more rapidly and with higher turbidity this is our control site in the paired watershed experiment that we did at el coronado ranch the results were in and the data confirmed dr norman's suspicions of the benefits of rock detention structures the first result of the hydrologic discharge analysis showed the watershed treated with rock detention structures having a 50 reduced average rate of flow mainly during

flash flood events in addition the check dams were found to be extending the timing of summer base flows in the treated watershed by three to four weeks the result that was maybe the most shocking was that there was 28 percent more water flowing downstream in the treated watershed when compared to the control watershed of rock creek this goes against conventionally held beliefs that bare bedrock transports more water downstream what the evidence portrays instead is that these rock detention structures are allowing more water to be kept in the system dr norman's team hypothesized that the czech

dams were creating perched water tables above bedrock a calibrated soil and water model was applied to estimate the total soil stored by check dams throughout the watershed and it found that they stored a little more than 200 tons per year this erosion control around the check dams keeps the sediment out of the stream and increases downstream water quality the results of the soil isotope analysis depicted the potential rate of carbon capture for rock detention structures at between 200 and 250 metric tons per hectare which is equivalent to what is stored in coastal wetlands all of

these rock detention structures are detaining the water they're capturing the soil they're capturing what's proven to be very rich nutrient-rich soil they're sequestering carbon and they're allowing the water to stand still in these dirt sponges long enough so that the vegetation is able to take hold and then the vegetation then acts on the same cycle helping to delay the water and keep the sediment in place the usgs team's scientific approach to gathering data was able to verify the ecohydrologic benefits provided by restoring the landscape with rock detention structures the data showed that these structures bring

much needed water back into ecosystems store carbon and sediment on par with coastal wetlands support riparian habitat reduce erosion sediment yield and flow intensity and keep water in dry land streams longer than watersheds not treated with rock detention structures this installation of and research on rock detention structures in the turkey pen watershed introduces low-tech and low-cost climate mitigation and adaptation strategies paving the way for us to use natural infrastructure as a nature-based solution here in the chirikawa mountains and beyond if you are interested in learning more you can find links to the papers published from

this research and other resources mentioned throughout the video in the video's description section you