Posts for Tag: California

California is World’s 4th Largest Economy

Posted In: Economics
California fourth largest economy

This is one of an ongoing series of visualizations about the state of California. This one is about the state’s economy, which recently moved into 4th place (2024), if California were its own country. It is, however, still part of the United States.

The visualization shows the relative sizes of the top 10 world economies (including the US, with California removed for context). California has the smallest population of any of the top 10, with #9 Canada just barely larger than California in population, though with a significantly smaller sized economy (about 1/2 the size).

Hover over the countries to see their GDP and population. California is behind the United States, China and Germany in total economic output (in nominal terms), but ahead of much larger countries Japan and India and the United Kingdom.

The state’s economy produces $4.1 Trillion dollars of economic output, driven by a range of industries including technology, real estate, manufacturing, agriculture and health care. It is a hub for innovation and entrepreneurship. California is also the leading agricultural state in the United States. Immigration is a huge part of the state’s workforce.

Sources and Tools:
2024 economic data was downloaded from the International Monetary Fund (IMF). This visualization is made using d3.js, an open-source javascript visualization library.

World's Largest Economies

University of California Admission Rates by Major

Posted In: College

Which majors are most competitive across the University of California system?

The University of California consists of nine campuses with undergraduate programs and they are all ranked among the best universities in the US (according to US News). All nine rank within the top 45 public schools including #1 and #2 and top 85 national universities in the US.

This data visualization focuses on the acceptance rates for students based on their indicated preferred majors in their application to the various University of California campuses in the Fall of 2023 admissions cycle. When you apply to a given university campus, you need to specify a major and this choice can affect the student’s chances of getting accepted, especially if the major is very sought after. Subjects like computer science are very popular and as a result, the data shows that most campuses have a lower acceptance rate for computer science as compared to the university as a whole.

Data visualization

The graph shown in the data visualization is a marimekko graph which shows a percentage based bar graph showing the acceptance rate (in blue) for a given major at a given university. The height of each horizontal bar is proportional to the number of applicants to that major, so taller bars have more applicants vs bars that are shorter. If you hover over (or click on mobile) a bar, it provides more information about the acceptance rate, enrollment rate (i.e. yield rate) and the GPA of accepted students. You can choose to sort the graph by subject name, admit rate or number of applicants.

The data visualization can help you explore different campuses and major categories. If you are viewing “School View“, you can see how the various disciplines compare for a single university at one time. Whereas if you view “Subject View” you can see the comparison of a single discipline across the University campuses that offer those majors.

The University of California has over 240,000 undergraduate students and extends about 140,000 acceptances to fill out 42,000 slots for first year students. There is a significant amount of overlap as most students applying for admission apply to several campuses, and many students get accepted to multiple campuses.

The broad disciplines used in the visualization are composed of a number of individual majors and these are detailed in the table below.

 

GPA calculation

The University of California only considers grades from 10th grade and 11th grade for admissions decisions, and uses a weighted system where honors and AP classes are given an extra point in GPA calculations above the normal A=4, B=3, C=2, etc. . GPA calculation. So for an honors math class, for example, an A would be worth 5 points.

 

Sources and Tools:
Data comes directly from the University of California website for the fall of 2023, which has quite a bit of interesting data about students and admissions. I downloaded the data and processed it with python to organize it. The webtool is made using javascript, HTML and CSS and graphed using the open-source plotly graphing library.

 

Table of Disciplines to majors

This table lists the specific areas and majors that make up the broad disciplines shown in the data visualization.

Broad discipline CIP Family Title CIP Subfamily Title
Architecture ARCHITECTURE AND RELATED SERVICES Architecture.
Architecture ARCHITECTURE AND RELATED SERVICES City/Urban, Community, and Regional Planning.
Architecture ARCHITECTURE AND RELATED SERVICES Environmental Design.
Architecture ARCHITECTURE AND RELATED SERVICES Landscape Architecture.
Architecture ARCHITECTURE AND RELATED SERVICES Real Estate Development.
Arts & Humanities FOREIGN LANGUAGES, LITERATURES, AND LINGUISTICS Linguistic, Comparative, and Related Language Studies and Services.
Arts & Humanities FOREIGN LANGUAGES, LITERATURES, AND LINGUISTICS African Languages, Literatures, and Linguistics.
Arts & Humanities FOREIGN LANGUAGES, LITERATURES, AND LINGUISTICS East Asian Languages, Literatures, and Linguistics.
Arts & Humanities FOREIGN LANGUAGES, LITERATURES, AND LINGUISTICS Slavic, Baltic and Albanian Languages, Literatures, and Linguistics.
Arts & Humanities FOREIGN LANGUAGES, LITERATURES, AND LINGUISTICS Germanic Languages, Literatures, and Linguistics.
Arts & Humanities FOREIGN LANGUAGES, LITERATURES, AND LINGUISTICS Romance Languages, Literatures, and Linguistics.
Arts & Humanities FOREIGN LANGUAGES, LITERATURES, AND LINGUISTICS Middle/Near Eastern and Semitic Languages, Literatures, and Linguistics.
Arts & Humanities FOREIGN LANGUAGES, LITERATURES, AND LINGUISTICS Classics and Classical Languages, Literatures, and Linguistics.
Arts & Humanities FOREIGN LANGUAGES, LITERATURES, AND LINGUISTICS Celtic Languages, Literatures, and Linguistics.
Arts & Humanities FOREIGN LANGUAGES, LITERATURES, AND LINGUISTICS Foreign Languages, Literatures, and Linguistics, Other.
Arts & Humanities ENGLISH LANGUAGE AND LITERATURE/LETTERS English Language and Literature, General.
Arts & Humanities ENGLISH LANGUAGE AND LITERATURE/LETTERS Rhetoric and Composition/Writing Studies.
Arts & Humanities ENGLISH LANGUAGE AND LITERATURE/LETTERS Literature.
Arts & Humanities ENGLISH LANGUAGE AND LITERATURE/LETTERS English Language and Literature/Letters, Other.
Arts & Humanities LIBERAL ARTS AND SCIENCES, GENERAL STUDIES AND HUMANITIES Liberal Arts and Sciences, General Studies and Humanities.
Arts & Humanities PHILOSOPHY AND RELIGIOUS STUDIES Philosophy.
Arts & Humanities PHILOSOPHY AND RELIGIOUS STUDIES Religion/Religious Studies.
Arts & Humanities VISUAL AND PERFORMING ARTS Visual and Performing Arts, General.
Arts & Humanities VISUAL AND PERFORMING ARTS Dance.
Arts & Humanities VISUAL AND PERFORMING ARTS Design and Applied Arts.
Arts & Humanities VISUAL AND PERFORMING ARTS Drama/Theatre Arts and Stagecraft.
Arts & Humanities VISUAL AND PERFORMING ARTS Film/Video and Photographic Arts.
Arts & Humanities VISUAL AND PERFORMING ARTS Fine and Studio Arts.
Arts & Humanities VISUAL AND PERFORMING ARTS Music.
Arts & Humanities VISUAL AND PERFORMING ARTS Arts, Entertainment, and Media Management.
Arts & Humanities VISUAL AND PERFORMING ARTS Visual and Performing Arts, Other.
Arts & Humanities HISTORY History.
Broad discipline CIP Family Title CIP Subfamily Title
Business BUSINESS, MANAGEMENT, MARKETING, AND RELATED SUPPORT SERVICES Business Administration, Management and Operations.
Business BUSINESS, MANAGEMENT, MARKETING, AND RELATED SUPPORT SERVICES Business/Managerial Economics.
Business BUSINESS, MANAGEMENT, MARKETING, AND RELATED SUPPORT SERVICES Human Resources Management and Services.
Business BUSINESS, MANAGEMENT, MARKETING, AND RELATED SUPPORT SERVICES Management Information Systems and Services.
Business BUSINESS, MANAGEMENT, MARKETING, AND RELATED SUPPORT SERVICES Management Sciences and Quantitative Methods.
Computer Science COMPUTER AND INFORMATION SCIENCES AND SUPPORT SERVICES Computer and Information Sciences, General.
Computer Science COMPUTER AND INFORMATION SCIENCES AND SUPPORT SERVICES Computer Programming.
Computer Science COMPUTER AND INFORMATION SCIENCES AND SUPPORT SERVICES Information Science/Studies.
Computer Science COMPUTER AND INFORMATION SCIENCES AND SUPPORT SERVICES Computer Science.
Computer Science COMPUTER AND INFORMATION SCIENCES AND SUPPORT SERVICES Computer Software and Media Applications.
Computer Science COMPUTER AND INFORMATION SCIENCES AND SUPPORT SERVICES Computer/Information Technology Administration and Management.
Education EDUCATION Education, General.
Education EDUCATION Social and Philosophical Foundations of Education.
Education EDUCATION Special Education and Teaching.
Education EDUCATION Teacher Education and Professional Development, Specific Subject Areas.
Engineering ENGINEERING Engineering, General.
Engineering ENGINEERING Aerospace, Aeronautical, and Astronautical/Space Engineering.
Engineering ENGINEERING Agricultural Engineering.
Engineering ENGINEERING Biomedical/Medical Engineering.
Engineering ENGINEERING Chemical Engineering.
Engineering ENGINEERING Civil Engineering.
Engineering ENGINEERING Computer Engineering.
Engineering ENGINEERING Electrical, Electronics, and Communications Engineering.
Engineering ENGINEERING Engineering Physics.
Engineering ENGINEERING Engineering Science.
Engineering ENGINEERING Environmental/Environmental Health Engineering.
Engineering ENGINEERING Materials Engineering.
Engineering ENGINEERING Mechanical Engineering.
Engineering ENGINEERING Nuclear Engineering.
Engineering ENGINEERING Operations Research.
Engineering ENGINEERING Geological/Geophysical Engineering.
Engineering ENGINEERING Mechatronics, Robotics, and Automation Engineering.
Engineering ENGINEERING Biochemical Engineering.
Engineering ENGINEERING Biological/Biosystems Engineering.
Engineering ENGINEERING Engineering, Other.
Life Sciences AGRICULTURAL/ ANIMAL/ PLANT/ VETERINARY SCIENCE AND RELATED FIELDS Animal Sciences.
Life Sciences AGRICULTURAL/ ANIMAL/ PLANT/ VETERINARY SCIENCE AND RELATED FIELDS Food Science and Technology.
Life Sciences AGRICULTURAL/ ANIMAL/ PLANT/ VETERINARY SCIENCE AND RELATED FIELDS Plant Sciences.
Life Sciences NATURAL RESOURCES AND CONSERVATION Natural Resources Conservation and Research.
Life Sciences NATURAL RESOURCES AND CONSERVATION Forestry.
Life Sciences NATURAL RESOURCES AND CONSERVATION Wildlife and Wildlands Science and Management.
Life Sciences NATURAL RESOURCES AND CONSERVATION Natural Resources and Conservation, Other.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Biology, General.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Biochemistry, Biophysics and Molecular Biology.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Botany/Plant Biology.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Cell/Cellular Biology and Anatomical Sciences.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Microbiological Sciences and Immunology.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Zoology/Animal Biology.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Genetics.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Physiology, Pathology and Related Sciences.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Pharmacology and Toxicology.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Biomathematics, Bioinformatics, and Computational Biology.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Biotechnology.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Ecology, Evolution, Systematics, and Population Biology.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Neurobiology and Neurosciences.
Life Sciences BIOLOGICAL AND BIOMEDICAL SCIENCES Biological and Biomedical Sciences, Other.
Broad discipline CIP Family Title CIP Subfamily Title
Nursing HEALTH PROFESSIONS AND RELATED PROGRAMS Registered Nursing, Nursing Administration, Nursing Research and Clinical
Other Health Science HEALTH PROFESSIONS AND RELATED PROGRAMS Pharmacy, Pharmaceutical Sciences, and Administration.
Other Health Science HEALTH PROFESSIONS AND RELATED PROGRAMS Public Health.
Other/ Interdisciplinary AGRICULTURAL/ ANIMAL/ PLANT/ VETERINARY SCIENCE AND RELATED FIELDS Agricultural Business and Management.
Other/ Interdisciplinary AGRICULTURAL/ ANIMAL/ PLANT/ VETERINARY SCIENCE AND RELATED FIELDS Agricultural Production Operations.
Other/ Interdisciplinary AGRICULTURAL/ ANIMAL/ PLANT/ VETERINARY SCIENCE AND RELATED FIELDS International Agriculture.
Other/ Interdisciplinary COMMUNICATION, JOURNALISM, AND RELATED PROGRAMS Communication and Media Studies.
Other/ Interdisciplinary COMMUNICATION, JOURNALISM, AND RELATED PROGRAMS Journalism.
Other/ Interdisciplinary LEGAL PROFESSIONS AND STUDIES Non-Professional Legal Studies.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Peace Studies and Conflict Resolution.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Mathematics and Computer Science.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Medieval and Renaissance Studies.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Science, Technology and Society.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Nutrition Sciences.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES International/Globalization Studies.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Classical and Ancient Studies.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Cognitive Science.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Human Biology.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Marine Sciences.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Sustainability Studies.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Geography and Environmental Studies.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Data Science.
Other/ Interdisciplinary MULTI/INTERDISCIPLINARY STUDIES Multi/Interdisciplinary Studies, Other.
Pharmacy HEALTH PROFESSIONS AND RELATED PROGRAMS Pharmacy, Pharmaceutical Sciences, and Administration.
Physical Sciences/Math MATHEMATICS AND STATISTICS Mathematics.
Physical Sciences/Math MATHEMATICS AND STATISTICS Applied Mathematics.
Physical Sciences/Math MATHEMATICS AND STATISTICS Statistics.
Physical Sciences/Math PHYSICAL SCIENCES Astronomy and Astrophysics.
Physical Sciences/Math PHYSICAL SCIENCES Atmospheric Sciences and Meteorology.
Physical Sciences/Math PHYSICAL SCIENCES Chemistry.
Physical Sciences/Math PHYSICAL SCIENCES Geological and Earth Sciences/Geosciences.
Physical Sciences/Math PHYSICAL SCIENCES Physics.
Physical Sciences/Math PHYSICAL SCIENCES Materials Sciences.
Physical Sciences/Math PHYSICAL SCIENCES Physical Sciences, Other.
Broad discipline CIP Family Title CIP Subfamily Title
Public Admin PUBLIC ADMINISTRATION AND SOCIAL SERVICE PROFESSIONS Community Organization and Advocacy.
Public Admin PUBLIC ADMINISTRATION AND SOCIAL SERVICE PROFESSIONS Public Administration.
Public Admin PUBLIC ADMINISTRATION AND SOCIAL SERVICE PROFESSIONS Public Policy Analysis.
Public Admin PUBLIC ADMINISTRATION AND SOCIAL SERVICE PROFESSIONS Social Work.
Public Admin PUBLIC ADMINISTRATION AND SOCIAL SERVICE PROFESSIONS Public Administration and Social Service Professions, Other.
Public Health HEALTH PROFESSIONS AND RELATED PROGRAMS Public Health.
Social Sciences AGRICULTURAL/ANIMAL/ PLANT/VETERINARY SCIENCE AND RELATED FIELDS Agricultural Business and Management.
Social Sciences AREA, ETHNIC, CULTURAL, GENDER, AND GROUP STUDIES Area Studies.
Social Sciences AREA, ETHNIC, CULTURAL, GENDER, AND GROUP STUDIES Ethnic, Cultural Minority, Gender, and Group Studies.
Social Sciences AREA, ETHNIC, CULTURAL, GENDER, AND GROUP STUDIES Area, Ethnic, Cultural, Gender, and Group Studies, Other.
Social Sciences FAMILY AND CONSUMER SCIENCES/HUMAN SCIENCES Human Development, Family Studies, and Related Services.
Social Sciences FAMILY AND CONSUMER SCIENCES/HUMAN SCIENCES Apparel and Textiles.
Social Sciences PSYCHOLOGY Psychology, General.
Social Sciences PSYCHOLOGY Research and Experimental Psychology.
Social Sciences PSYCHOLOGY Clinical, Counseling and Applied Psychology.
Social Sciences PSYCHOLOGY Psychology, Other.
Social Sciences SOCIAL SCIENCES Social Sciences, General.
Social Sciences SOCIAL SCIENCES Anthropology.
Social Sciences SOCIAL SCIENCES Archeology.
Social Sciences SOCIAL SCIENCES Criminology.
Social Sciences SOCIAL SCIENCES Economics.
Social Sciences SOCIAL SCIENCES Geography and Cartography.
Social Sciences SOCIAL SCIENCES International Relations and National Security Studies.
Social Sciences SOCIAL SCIENCES Political Science and Government.
Social Sciences SOCIAL SCIENCES Sociology.
Social Sciences SOCIAL SCIENCES Urban Studies/Affairs.
Social Sciences SOCIAL SCIENCES Social Sciences, Other.

UC admissions by major

California Electricity Generation

Posted In: Energy | Environment
California Electricity Generation

What are the main sources of California’s electricity?

I added the option to view the graph for any day or monthly average from April 2018 to the present using the calendar picker and a daily generation summary

In the United States, electric power plant emissions account for about 25% of greenhouse gas emissions. However, California has been a leader in the transition to clean and renewable energy, driven by ambitious climate policies and a commitment to reducing greenhouse gas emissions. The state has set an electricity target for the state of 60% renewables by 2030 and 100% zero-carbon, clean electricity by 2045. To meet these targets, the state has been investing heavily into solar and wind energy sources. Solar is the largest proportion of California’s electricity grid and California now generates more solar energy than any other state.

The California Independent System Operator manages the grid for around 32 million Californians or about 80% of the total demand in the state. Here is a map showing the service area and the other electricity districts in the state, the main exceptions include the city of LA and the Sacramento area.

How to read the graph of California’s electricity

The graphs shown here allow us to visualize how electricity generation in the California Independent System Operator (CAISO) region varies over the course of the day. We can see how solar ramps up to be a huge contributor in the middle of the day. And overall, the vast majority of the generation in the state is one form of renewable electricity or another (e.g. solar, wind, hydro, geothermal, biomass and biogas). Add in a small contribution from zero-carbon nuclear energy and we can see that a large majority of power generation comes from zero-carbon sources. It also shows the total electricity demand, which should always be less than the total electricity supply in the state.

Because of the intermittent nature of some renewables, like wind and solar, there are times where the demand for electricity is not able to be met by these sources, and other options are needed to maintain supply demand balance on the state’s grid. To address this issue, the state relies on importing power from outside of the state as well as energy storage (primarily batteries) to meet electricity demand when renewable energy supply is low. If demand is much less than supply, then likely there will be power exported or some charging of batteries. And if demand is less than total generation in the state, power will be imported and/or batteries will be discharged to make up for the power shortfall.

On the graph, positive values from batteries and imports is when those sources are supplying power to the California grid. Negative values for batteries and exports are when there is excess power in the state and batteries are being charged up or power is being exported to neighboring states.

You can view the graph in two forms:

  • Detailed – shows all of the power plant fuel types that is provided in the CAISO data: Solar, Wind, Nuclear, Coal, Other, Natural Gas, Large Hydropower, Small Hydropower, Geothermal, Biomass and Biogas. In addition, it shows aggregated net imports into the state from other regions as well as battery discharging or charging.
  • Simplified – I aggregated the categories from CAISO into Solar, Wind, Nuclear, Fossil Fuel (including Coal, Other and Natural Gas), Hydro (Large and Small Hydropower), and Other Renewable (Geothermal, Biomass and Biogas). In addition, it shows aggregated net imports into the state from other regions as well as battery discharging or charging.

Also, I added the ability to see yesterday’s data as well. In the future, I will add the ability to see other dates as well.

Data Sources and Tools
Data for electricity sources for California grid comes from the California Independent System Operator (CAISO). This data from this site is downloaded and processed using a python script and updated every 5 minutes. The graph is made using the open source Plotly javascript graphing library.

California Electricity Generation

Tioga Pass (Yosemite) Opening Dates

Posted In: Environment | Water

When does Tioga Pass in Yosemite typically open?

The graph shows the closing and opening dates of Tioga pass in Yosemite National Park for each winter season from 1933 to the present. Tioga pass is a mountain pass on State Highway 120 in California’s Sierra Nevada mountain range and one of the entrances to Yosemite NP. The pass itself peaks at 9945 ft above sea level. Each winter it gets a ton of snow, but also with a great deal of variability, which really affects when it can be plowed and the road reopened.

Our family likes to go to Yosemite in June after the kids school lets out and sometimes Hwy 120 and Tioga Pass can often be closed at this time, which limits which areas of the park you can visit. So I often look at data on when the road has opened before and thought it would be a good thing to visualize.

You can toggle the labels on the graph that show the dates of opening and closing as well as the number of days that the pass was closed each winter. Hovering (or clicking) on the circles on the graph will give you a pop up which gives you the exact date.

Data and Tools
The data comes from the US National Park Service for most recent data as well as Mono Basin Clearinghouse for earlier data going back to 1933. Data was organized and compiled in MS Excel. Visualization was done in javascript and specifically the plotly visualization library.

tioga pass opening date

Colorado River Reservoir Levels

Posted In: Environment | Water

How much water is in the main Colorado River reservoirs?

Check out my California Reservoir Levels Dashboard
 

I based this graph off of my California Reservoir marimekko graph, because many folks were interested in seeing a similar figure for the Colorado river reservoirs.

This is a marimekko (or mekko) graph which may take some time to understand if you aren’t used to seeing them. Each “row” represents one reservoir, with bars showing how much of the reservoir is filled (blue) and unfilled (brown). The height of the “row” indicates how much water the reservoir could hold. Lake Mead is the reservoir with the largest capacity (at almost 29,000 kaf) and so it is the tallest row. The proportion of blue to brown will show how full it is. As with the California version of this graph, there are also lines that represent historical levels, including historical median level for the day of the year (in red) and the 1 year ago level, which is shown as a dark blue line. I also added the “Deadpool” level for the two largest reservoirs. This is the level at which water cannot flow past the dam and is stuck in the reservoir.

Lake Mead and Lake Powell are by far the largest of these reservoirs and also included are several smaller reservoirs (relative to these two) so the bars will be very thin to the point where they are barely a sliver or may not even show up.

Historical Data

Historical data comes from https://www.water-data.com/ and differs for each reservoir.

  • Lake Mead – 1941 to 2015
  • Lake Powell – 1964 to 2015
  • Flaming Gorge – 1972 to 2015
  • Lake Mohave – 1952 to 2015
  • Lake Navajo – 1969 to 2015
  • Blue Mesa – 1969 to 2015
  • Lake Havasu – 1939 to 2015

The daily data for each reservoir was captured in this time period and median value for each day of the calendar year was calculated and this is shown as the red line on the graph.

Instructions:
If you are on a computer, you can hover your cursor over a reservoir and the dashboard at the top will provide information about that individual reservoir. If you are on a mobile device you can tap the reservoir to get that same info. It’s not possible to see or really interact with the tiniest slivers. The main goal of this visualization is to provide a quick overview of the status of the main reservoirs along the Colorado River (or that provide water to the Colorado).

Units are in kaf, thousands of acre feet. 1 kaf is the amount of water that would cover 1 acre in one thousand feet of water (or 1000 acres in water in 1 foot of water). It is also the amount of water in a cube that is 352 feet per side (about the length of a football field). Lake Mead is very large and could hold about 35 cubic kilometers of water at full (but not flood) capacity.

Data and Tools
The data on water storage comes from the US Bureau of Reclamation’s Lower Colorado River Water Operations website. Historical reservoir levels comes from the water-data.com website. Python is used to extract the data and wrangle the data in to a clean format, using the Pandas data analysis library. Visualization was done in javascript and specifically the D3.js visualization library.

colorado river reservoir levels dashboard

Visualizing California’s Water Storage – Reservoirs and Snowpack

Posted In: Environment | Water
California reservoirs and snowpack visualization

How much water is stored in California’s snowpack and reservoirs?

California’s snow pack is essentially another “reservoir” that is able to store water in the Sierra Nevada mountains. Graphing these things together can give a better picture of the state of California’s water and drought.

The historical median (i.e. 50th percentile) for snow pack water content is stacked on top of the median for reservoirs storage (shown in two shades of blue).  The current water year reservoirs is shown in orange and the current year’s snow pack measurement is stacked on top in green.  What is interesting is that the typical peak snow pack (around April 1) holds almost as much water (about 2/3 as much) as the reservoirs typically do.  However, the reservoirs can store these volumes for much of the year while the snow pack is very seasonal and only does so for a short period of time.

Snowpack is measured at 125 different snow sensor sites throughout the Sierra Nevada mountains. The reservoir value is the total of 50 of the largest reservoirs in California.  In both cases, the median is derived from calculating the median values for each day of the year from historical data from these locations from 1970 to 2021.

I’ve been slowly building out the water tracking visualizations tools/dashboards on this site. And with the recent rains (January 2023), there has been quite a bit of interest in these visualizations.  One data visualization that I’ve wanted to create is to combine the precipitation and reservoir data into one overarching figure.

Creating the graph

I recently saw one such figure on Twitter by Mike Dettinger, a researcher who studies water/climate issues. The graph shows the current reservoir and snowpack water content overlaid on the historic levels.  It is a great graph that conveys quite a bit of info and I thought I would create an interactive version of these while utilizing the automated data processing that’d I’d already created to make my other graphs/dashboards.

The challenge was to convert inches of snow water equivalent into a total volume of water in the snowpack, which I asked Mike about. He pointed me to a paper by Margulis et al 2016 that estimates the total volume of water in the Sierra snowpack for 31 years.  Since I already had downloaded data on historical snow water equivalents for these same years, I could correlate the estimated peak snow water volume (in cubic km) to the inches of water at these 120 or so Sierra snow sensor sites.  I ran a linear regression on these 30 data points. This allowed me to estimate a scaling factor that converts the inches of water equivalent to a volume of liquid water (and convert to thousands of acre feet, which is the same unit as reservoirs are measured in).

California Snow Visualization

This scaling factor allows me to then graph the snowpack water volume with the reservoir volumes.

See my snowpack visualization/post to see more about snow water equivalents.

My numbers may differ slightly from the numbers reported on the state’s website. The historical percentiles that I calculated are from 1970 until 2020 while I notice the state’s average is between 1990 and 2020.

You can hover (or click) on the graph to audit the data a little more clearly.

Sources and Tools

Data is downloaded from the California Data Exchange Center website of the California Department of Water Resources using a python script. The data is processed in javascript and visualized here using HTML, CSS and javascript and the open source Plotly javascript graphing library.

California Snow Visualization