Investigating the Link Between Surface Water and Groundwater in the Tule Lake Subbasin, Oregon and California

Portland State University | August 13th, 2014

Water allocation in the upper Klamath Basin of Oregon and California has been challenging. Irrigators have increasingly turned to groundwater to make up for surf

Water allocation in the upper Klamath Basin of Oregon and California has been challenging. Irrigators have increasingly turned to groundwater to make up for surface water shortages because of shifts in allocation toward in-stream flows for Endangered Species Act-listed fishes. The largest increase in groundwater pumping has been in and around the Bureau of Reclamation’s Klamath Irrigation Project, which includes the Tule Lake subbasin in the southern part of the upper Klamath Basin. Previous groundwater flow model simulations indicate that water level declines from pumping may result in decreased flow to agricultural drains in the Tule Lake subbasin. Agricultural drains on the Klamath Project are an important source of water for downstream irrigators and for the Tule Lake and Lower Klamath Lake National Wildlife Refuges. To better assess the impact of increased pumping on drain flow and on the water balance of the groundwater system, flow data from agricultural drains were evaluated to investigate the changes that have taken place in groundwater discharge to drains since pumping volumes increased. Additionally, a fine-grid groundwater model of the Tule Lake subbasin was developed based on the existing regional flow model. The fine-grid model has sufficient vertical and horizontal resolution to simulate vertical head gradients, takes advantage of time-series data from 38 observation wells for model calibration, and allows agricultural drains to be more explicitly represented. Results of the drain flow analysis show that the groundwater discharge to agricultural drains has decreased by approximately 4000 hectare-meters from the 1997-2000 average discharge. Most of this decrease takes place in the northern and southeastern portions of the subbasin.  Results of the groundwater model show that the initial source of water to wells is groundwater storage. By 2006, approximately 56% of the water from wells is sourced from agricultural drains.

Investigating the Role of Snow Water Equivalent on Streamflow Predictability during Drought

American Meteorological Society (AMS) | October 20th, 2022

Snowpack provides the majority of predictive information for water supply forecasts (WSFs) in snow-dominated basins across the western United States. Drought conditions t

Snowpack provides the majority of predictive information for water supply forecasts (WSFs) in snow-dominated basins across the western United States. Drought conditions typically accompany decreased snowpack and lowered runoff efficiency, negatively impacting WSFs. Here, we investigate the relationship between snow water equivalent (SWE) and April–July streamflow volume (AMJJ-V) during drought in small headwater catchments, using observations from 31 USGS streamflow gauges and 54 SNOTEL stations. A linear regression approach is used to evaluate forecast skill under different historical climatologies used for model fitting, as well as with different forecast dates. Experiments are constructed in which extreme hydrological drought years are withheld from model training, that is, years with AMJJ-V below the 15th percentile. Subsets of the remaining years are used for model fitting to understand how the climatology of different training subsets impacts forecasts of extreme drought years. We generally report overprediction in drought years. However, training the forecast model on drier years, that is, below-median years (P15, P57.5], minimizes residuals by an average of 10%in drought year forecasts, relative to a baseline case, with the highest median skill obtained in mid- to late April for colder regions. We report similar findings using a modified National Resources Conservation Service (NRCS) procedure in nine large Upper Colorado River basin (UCRB) basins, highlighting the importance of the snowpack–streamflow relationship in streamflow predictability. We propose an “adaptive sampling” approach of dynamically selecting training years based on antecedent SWE conditions, showing error reductions of up to 20% in historical drought years relative to the period of record. These alternate training protocols provide opportunities for addressing the challenges of future drought risk to water supply planning.

Klamath/San Joaquin/Sacramento Hydroclimatic Reconstructions from Tree Rings

California Department of Water Resources (DWR) | February 7th, 2014

This is a draft final report for Agreement Number 4600008850, “Klamath/San Joaquin/Sacramento Hydroclimatic Reconstructions”, signed October 13, 2010.  Work includes

This is a draft final report for Agreement Number 4600008850, “Klamath/San Joaquin/Sacramento Hydroclimatic Reconstructions”, signed October 13, 2010.  Work includes developing new and updated tree-ring chronologies, reconstructing specified streamflow and/or precipitation records in the Klamath, San Joaquin and Sacramento River Basins, and analyzing the time series properties of the reconstructions. These reconstructions allow assessment of hydrologic variability over centuries to millennia and give context for assessing recent drought events. Tasks on this project included field collections; laboratory work in sample preparation, dating and measurement; and statistical work in chronology development, reconstruction, and analysis of those reconstructions. The interpretation of the reconstructions includes five main components : 1) place instrumental-period flow statistics in a long-term context, 2) quantify droughts and wet periods, 3) identify cycles in wetness and dryness, 4) check consistency with other paleoclimatic data, and 5) assess reconstructed flow variations in the context of expected scenarios of climate. A total of 16 different hydroclimatic series – 11 flow records and 5 precipitation records, were reconstructed. This report summarizes the research project products and results. The Data and Methods section of this report describes the field collections and development of tree-ring chronologies, reconstruction modeling, and methods of analyzing reconstructions. The Results section focuses on the interpretation of selected key reconstructions for the Klamath, Sacramento, and San Joaquin basins. Annual time series of the 16 reconstructions are included as products in an appendix and in a digital spreadsheet.

Land use and land cover influence on water quality in the last free-flowing river draining the western Sierra Nevada, California

Journal of Hydrology (Elsevier) | November 10th, 2005

Land use and land cover across 28 sub-basins within the Cosumnes Watershed, CA (1989 km2) were correlated to nitrate-N and total suspended solids (TSS) loading between w

Land use and land cover across 28 sub-basins within the Cosumnes Watershed, CA (1989 km2) were correlated to nitrate-N and total suspended solids (TSS) loading between water years 1999 and 2001. The impact of human development on stream water quality was evident as both agricultural area and population density predicted TSS loading in a linear mixed effects model. In contrast to the TSS model, the nitrate-N loading model was more complex with agriculture, grassland, and the presence or absence of waste water treatment plants (WWTPs) all contributing. The lack of correlation between population density and nitrate-N loading indicates that human habitation of the landscape does not impact stream nitrate levels until a WWTP is built within the sub-basin. During dry water years the models predict a linear reduction in TSS loading but the correlations to agriculture and population density remain positive. In contrast, nitrate is positively correlated to grasslands during average water years and negatively correlated during dry water years. Analysis of constituent fluxes from the upper watershed versus the lower watershed indicates that silica is derived primarily from the uplands and that during dry water years the upper watershed is an important source of dissolved organic carbon (DOC) and nitrate. The lower watershed contributes the majority of the sediment and nutrients during both dry and average water years, the one caveat being that during dry years the lower basin becomes a nitrate sink.

Landscape Patterns and Processes of the McCormack-Williamson Tract and Surrounding Area: A framework for restoring a resilient and functional landscape

San Francisco Estuary Institute (SFEI) | March 25th, 2013

This report uses a reconstruction of the historical (early 19th century) Sacramento-San Joaquin Delta landscape in concert with contemporary data to elucidate restoration

This report uses a reconstruction of the historical (early 19th century) Sacramento-San Joaquin Delta landscape in concert with contemporary data to elucidate restoration opportunities and constraints at the McCormack-Williamson Tract and within the surrounding Delta setting. Historical ecology encourages a landscape-level perspective of restoration through improved understanding of how physical processes created and maintained habitat mosaics in the recent past. This perception of landscapes can be used to evaluate current conditions and develop future restoration scenarios. We used the recently completed study of the historical Delta landscape (Whipple et al. 2012) to explore opportunities for the McCormack-Williamson Tract (MWT), a 1,645 acre (6.6 km2) tract along the Mokelumne River (Figure 1 and Figure 2). This site exemplifies the need to balance contemporary constraints to restoration (including existing infrastructure and flood protection concerns) with the goals of landscape-scale restoration. To explore some of the strategies and opportunities available to advance the landscape-scale restoration in the MWT area, three general concepts emerged: increasing landscape complexity, connectivity, and resilience. To understand how to interpret and improve these attributes, we developed conceptual models that placed the site within the larger landscapes of the historical Delta, relating local habitat features to regional controlling physical gradients. This aided interpretation of the contemporary physical landscape and allowed identification of opportunities and constraints to both short-term and long-term landscape-scale restoration. The historical record reveals features such as floodplain lakes, forests on natural river levees, and tidal channels in the study area. These and other features could be strategically incorporated into a restoration vision, or an “operational landscape unit” for this part of the Delta (Verhoeven et al. 2008). This type of perspective can help focus restoration targets, including the relative proportion and placement of different habitat types and landscape elements within project design constraints, maximizing the site’s ecological potential. The landscape-scale approach also identifies opportunities to improve ecological connectivity and long-term adaptability to sea level rise and other environmental changes. Some of these opportunities may be critical to the ecological function and resilience of the area, but may not be able to be addressed in the immediate MWT project design. Thus, a central component of translating a historical landscape perspective to site-scale design is envisioning an adaptable restoration process that spans short-term restoration actions that are possible within the site’s bounds, while maintaining a longer-term vision of what is needed at the landscape scale.

Landslide-channel feedbacks amplify channel widening during floods

Nature Portfolio (Springer Nature) | January 24th, 2025

Large contribution from anthropogenic warming to an emerging North American megadrought

American Association for the Advancement of Science (AAAS) | April 17th, 2020

Severe and persistent 21st-century drought in southwestern North America (SWNA) motivates comparisons to medieval megadroughts and questions about the role of anthropogen

Severe and persistent 21st-century drought in southwestern North America (SWNA) motivates comparisons to medieval megadroughts and questions about the role of anthropogenic climate change. We use hydrological modeling and new 1200-year tree-ring reconstructions of summer soil moisture to demonstrate that the 2000–2018 SWNA drought was the second driest 19-year period since 800 CE, exceeded only by a late-1500s megadrought. The megadrought-like trajectory of 2000–2018 soil moisture was driven by natural variability superimposed on drying due to anthropogenic warming. Anthropogenic trends in temperature, relative humidity, and precipitation estimated from 31 climate models account for 47% (model interquartiles of 35 to 105%) of the 2000–2018 drought severity, pushing an otherwise moderate drought onto a trajectory comparable to the worst SWNA megadroughts since 800 CE.

Large Landscape Urban Irrigation: A Data‐Driven Approach to Evaluate Conservation Behavior

American Geophysical Union (AGU) | April 30th, 2019

Do businesses, multifamily residences, and homeowners associations irrigate differently than single‐family residences? Do customers who have recycled water irrigate di

Do businesses, multifamily residences, and homeowners associations irrigate differently than single‐family residences? Do customers who have recycled water irrigate differently than if they have potable water? How does water use change during drought and under different policy regimes? Is neighborhood affluence related to conservation behavior by nonresidential irrigation customers? These questions are all important for water managers planning how much water they need when and where, in the present and in the future. In this paper, we statistically investigated and modeled water use in a case study service area to examine how water demand for nonresidential large landscapes changed during a historic drought. The findings of this paper can help water managers understand urban water use behavior, which is useful for supply planning, targeting conservation efforts, and optimizing infrastructure investment.

Large Landscape Urban Irrigation: A Data‐Driven Approach to Evaluate Conservation Behavior

American Geophysical Union (AGU) | January 30th, 2019

Do businesses, multifamily residences, and homeowners associations irrigate differently than single‐family residences? Do customers who have recycled water irrigate di

Do businesses, multifamily residences, and homeowners associations irrigate differently than single‐family residences? Do customers who have recycled water irrigate differently than if they have potable water? How does water use change during drought and under different policy regimes? Is neighborhood affluence related to conservation behavior by nonresidential irrigation customers? These questions are all important for water managers planning how much water they need when and where, in the present and in the future. In this paper, we statistically investigated and modeled water use in a case study service area to examine how water demand for nonresidential large landscapes changed during a historic drought. The findings of this paper can help water managers understand urban water use behavior, which is useful for supply planning, targeting conservation efforts, and optimizing infrastructure investment.

Lessons from Immersive Online Collaborative Modeling to Discuss More Adaptive Reservoir Operations

American Society of Civil Engineers (ASCE) | April 26th, 2024