This dataset provides population estimate trends from 1998 to the current year for each of California’s 58 counties, further disaggregated by Detailed Analysis Units (DAUs) - the smallest geographic units historically used by the California Department of Water Resources for water planning as part of the California Water Plan. DAUs are subdivisions of Planning Areas and often align with county boundaries, although a single DAU may span multiple counties. They have traditionally supported water demand estimates based on crop and land use types.

The population estimates were developed using U.S. Bureau Census 2000, 2010 and 2020 data. Throughout the estimation process, intermediate results were reviewed and adjusted as needed, with professional judgment applied to smooth trends where appropriate.

Since the California Water Plan is retiring DAUs as its planning and analysis framework, future updates to this dataset will transition away from DAU based geography. Instead, population estimates will be provided based on other geographic units, such as the 8-digit Hydrologic Units (HUC8) defined by the U.S. Geological Survey’s Watershed Boundary Dataset.

A dashboard is available for visualizing historical population trends by county and DAU.

The study curates demographic information of a short-lived native iterocarpic herb, Cirsium undulatum. This data was collected from 1990 to 2009 at two study sites, Arapaho Prairie Preserves (APP) and Niobrara Valley Preserve (NVP), in the Nebraska Sandhills, USA. At APP, four 12m by 12m plots were established. At NVP, three 12m by 12m plots were established. The data associated with each plot are as described below:1. "UAASOverview19902009RAMET 20230630.xlsx" = Original Transition data for Plot A in APP2. "UABSOverview19902009RAMET 20230630.xlsx" = Original Transition data for Plot B in APP3. "UACSOverview19902009RAMET 20230630.xlsx" = Original Transition data for Plot C in APP4. "UADSOverview19902009RAMET 20230630.xlsx" = Original Transition data for Plot D in APP5. "UNMSOverview19902009RAMET 20230630.xlsx" = Original Transition data for Plot M in NVP6. "UNKSOverview19902009RAMET 20230630.xlsx" = Original Transition data for Plot K in NVP7. "UNLSOverview19902009RAMET 20230630.xlsx" = Original Transition data for Plot L in NVPIn 1990 – 1999, ramets in the plots were monitored twice a year: in early season (May) and in late season (late June - mid July); plots at both sites were examined within one week each year. In 4 years (2000 - 2004), all ramets were measured in late May, but in general, only flowering ramets were remeasured in July; however, some late-season observations were recorded on non-flowering ramets. In 5 years late in the study (2005 – 2009), the ramets were measured only once, in mid- to late-season: in mid-July for 3 years (2005 - 2007) and in late June for two years (2008 - 2009). New ramets observed in 2008 – 2009 at the end of the study were no longer given numerical tags; so, those did not contribute to the estimation of specific stage transition rates.This data is associated with a current ongoing project which examines the time-lag effect of weather variables on the vital rates of Cirsium undulatum. The data was collected by Dr. Svata Louda (a retired Professor from the School of Biological Sciences, University of Nebraska, Lincoln) with the help of her collaborators: A. Arnett, T. A. Rand, F. L. Russell, R. W. Otley, 18 graduate students, and 21 undergraduate students over the 20 years. The data provided here was extracted by Dr. Kathleen Keeler (also a retired Professor from the School of Biological Sciences, University of Nebraska, Lincoln) from the field data records.We want to acknowledge that this study was done on the homelands of the Lakota People (Arapaho Prairie Preserve) and of the Ponca People (Niobrara Valley Preserve); we honor this legacy. We are also indebted to The Nature Conservancy, Nebraska Chapter, for permission to work in these reserves and to their incredible staff for all of the support and encouragement provided for the study, especially A. A. Steuter at the beginning of the study.