The importance of the Colorado River cannot be overstated for the American West. The river and its tributaries serve more than 40 million people by providing drinking and municipal water. The water from the river basin irrigates more than 5 million acres of land, which produces around 15% of the nation’s crops. The dams in the basin generate 4,200 megawatts of hydro-power. Overall, the river system sustains over 16 million jobs, contributes $1.4 trillion per year to the economy, and supports terrestrial and aquatic ecosystems (USBR, 2012.)
Crystal Lake with San Juan mountains in the background near the Uncompahgre River – one of the tributaries of the Colorado River. Photo by M. Raffae
However, the current drought that has lingered for decades now poses a significant threat to everything that depends on the mighty Colorado River. The river basin lies in the region which is infamous for its natural variability. Over the course of history, the region has had cycles of dry and wet periods, which may also make the present drought look like a natural phenomenon alone. However, a study conducted in 2021 showed that around 19% of the current drought conditions can be attributed to human-induced climate change. Not only that, but the conditions are worse than they have been in at least 1200 years.
Since 90% of the streamflow in the Colorado River originates in the upper part of the basin,several studies over the years have focused on watershed modeling in that region many studies have investigated historical flows, while others have included baseflow – the steady release of groundwater that seeps into a stream or river. Some have gone further to use historical streamflow and baseflow to predict future conditions in the river basin using various climate models. However, almost all studies have either used pre-development scenarios – conditions when there was little to no water infrastructure such as dams, canals, levees, etc., management, and regulations – or have used oversimplified models that ignore the complexities of groundwater movement, storage, and interactions with the surface water.
The Colorado River Basin is one of the most highly regulated and over-allocated river systems in the world. As a result, basing studies on pre-development scenarios seems to be of little practical importance in this day of rapidly changing climate. Moreover, the importance of groundwater and its interactions with surface water cannot be ignored, as more than half of the streamflow in the basin is contributed by baseflow.
The river basin also has trans-basin or trans-mountain diversions. These diversions bring water from the western slope of the Rocky Mountains, which are in the Colorado River Basin, to the eastern slope of the Rockies outside of the basin. These diversions have also been ignored in previous models.
Map of the Colorado River Basin from USGS, 2016.
Therefore, my team, which includes my Ph.D. advisor at CSU, Associate Professor Ryan Bailey, and two scientists from the Agricultural Research Service, is working to address this knowledge gap by incorporating key hydrological processes that were overlooked in previous research studies. We are using a physically based and spatially distributed model to build and quantify historical streamflows and groundwater levels in the Upper Colorado River Basin for the post-development scenario. A physically based model simulates how water moves through the environment, using real-world processes, instead of relying on statistical patterns. A spatially distributed model, on the other hand, takes into account differences in the landscape and natural features across different areas. In our model, we have included reservoirs, canals, irrigation schedules, floodplains, trans-basin diversions, and tile drainage – an agricultural drainage system that removes excess subsurface water from irrigated fields. The model also simulates groundwater fluxes such as groundwater recharge, canal seepage, tile drainage flow, saturation excess flow, lake and reservoir seepage and evaporation, and groundwater-floodplain exchanges, which can be used to identify spatio-temporal patterns in the river basin.
Once we simulate the historical hydrology and fluxes, we plan to run what-if scenarios, hypothetical situations to help us analyze different options, for several water management, land use change, and climate change scenarios. This will allow us to come up with best management practices to address water issues and manage water resources more effectively and efficiently.
In the final phase of the study, we use what-if scenarios to assess the political and socio-economic aspects of the model. This includes, crop budgets, agricultural productivity in monetary terms, possibility and probability of Denver getting shut out from trans-mountain diversions in case of a drought, economic implications of sustainable groundwater use, the amount of water flowing at Lee’s Ferry in Arizona – the dividing point of the upper and lower basins, and so on.
The findings of this study can influence how water managers, government agencies, farmers, and other stakeholders approach water use and management for higher revenues and sustainability. Ecologists can gain insights into future streamflows and their potential impacts on aquatic ecosystems. Additionally, it will provide the scientific community with a solid foundation and valuable catalyst for future research. In the long run, these findings can help shape water policy, advancing the goal of achieving integrated regional water management.
The fate of the Colorado River Basin does not only depend on the climate and its variability, but also on the policies we create that define how we store, move, use, and manage our water. To come up with policies that help us sustain the economy, environment, and society, it is imperative that we conduct a comprehensive hydrological modeling study for the post-development scenario that shows us both our best- and worst-case scenarios for the future to better prepare for it. This study is an ambitious attempt to do so.
About the author: M. Raffae is a Ph.D. student in the Department of Civil and Environmental Engineering at Colorado State University (CSU) funded by the Fulbright Foreign Student scholarship program. He is also a fellow in the NSF Research Traineeship (NRT) Program InTERFEWS at CSU.
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