by Megan Nguyen

Which display is more engaging to you? The table or the map?

Crop Economics Web Map displaying information at the hydrologic region.

This table shows the total water use of each hydrologic region in California measured in Thousand Acre Feet.

Do you remember a time when you really needed to find something in your room that you know you for certain have but can’t remember where you placed it? And so then you have to search every nook and cranny of your room by hand? That’s what searching for online data feels like.

Data is the currency of science exchange and it is everywhere. As scientists, we deal with data constantly and are either collecting our own or searching for it. Government agencies produce a wealth of data and statistics collected from sensors, gauges, or sometimes simulated by models. However, finding this information is an arduous task as it is often buried deep within a website.

The data diggers are on a quest to find information! After traversing the many links on a website, we finally uncover the coveted data chest. We open it, expecting treasures, only to find ourselves presented with a library of zip files. These files have a secret code of numbers and letters and we are left to unlock their meaning with no cipher. But we can’t give up our search here! We must carry on with our mission. After many attempts, we manage to discover a common pattern between the file names and have unlocked their mystery. We manage to scavenge through the data chest and download what we need. After we process the raw data and refine our analysis, how do we share our data riches to the world? In other words, how do we display our data in a visually appealing manner?

The most common method used to display data is in static forms such as tables, graphs, and charts. Although widely used, a list of numbers in a table is not always the best way to get a message across. Dynamic displays that include color, graphics, or an interactive component can tell a story beyond a simple table or graph. One innovative method of dynamically displaying useful information in an engaging and attractive way is the use of interactive web maps. Web maps invite the user to take action in an interactive framework and explore the data on their own terms.

Our data voyage begins with an investigation into California’s irrigated agricultural use of land and water and its gross value. This information can be found on the California Department of Water Resources website. In its most basic form, the data is a set of excel spreadsheets which contain crop statistics as measured by the California DWR. This data set is consistent and well organized across years and spatial areas, which greatly facilitates translating it into a visual form. Instead of displaying these numbers in a table, Josué Medellin-Azura, Lawrence Li, and myself at the Center for Watershed Sciences recently published online the California Crop Economics Interactive Web Map. We chose to use a web map as an engaging display and invite users to freely explore the information.

Total water use of California at the detailed analysis unit level. Low to high values range from light to dark.

With one glance, a lot can be interpreted from this web map. By combining statistical data to GIS spatial data, we can associate statistics to the location they are related to on a map. As a result, the first thing that immediately stands out is the color gradient which shows the concentration of water usage or crop area based on color intensity. For example, in the map to the left you can see that the Central Valley has the highest total water usage which, makes sense as the Valley is a major hub of agricultural activity.

There are seven variables in the map: total water use, total irrigated crop area, applied water per acre, evapotranspiration of applied water per acre, total revenue, revenue per acre, and revenue per applied water. Each variable (except revenue variables which can only be viewed for revenue regions) can be viewed for different spatial analysis units (consistent with California Water Plan Update) that include, from largest to smallest: hydrologic region, planning area, detailed analysis unit, and revenue regions. The dataset only contains data for California from the years 1998-2010, and can be expanded to include years beyond 2010 when that data becomes available.

The web map has an user friendly interface that features toggle buttons for changing the analysis unit or variable shown as well as a slider to change years. Included in the map are text summary pop ups of each region and a gradient legend. By organizing data in an easily understandable and interactive graphic, a broader audience is able to engage with information in a way that makes it more meaningful, and increases general scientific literacy.

Explore the California Crop Economics Interactive Web Map for yourself!

Megan Nguyen is a GIS researcher at the Center for Watershed Sciences. Her work and interests  revolve around a variety of topics such as drought impacts, flood mitigation, environmental policy, and education outreach.