number and the watershed area. Withdrawal points are also independent geometry
elements stored in the spatial database.
A person utilizes the tool by clicking on a location of interest, such as a
watershed with a potential future withdrawal, to obtain spatial and tabular outputs.
When the user initiates the process by clicking in a watershed on the mapping
interface, a series of scripts are run to perform two major tasks. In the first task, the
system must correctly identify the watershed within which the user has clicked.
This is accomplished through a series of actions that select the smallest nested
watershed under the clicked point and the associated unique identification number.
The second task performed after a user clicks on the map is to return summary
information to the user interface about withdrawal and consumptive use within the
watershed. Using the unique ID of the selected watershed determined from the first
task, a series of additional JavaScript functions, Java Server Page scripts, and
Structured Query Language (SQL) statements are built and sent to the spatial
database to perform a spatial query of the withdrawal points contained within the
selected watershed and calculate the summary information. The spatial database
responds to these queries by returning the geometry of the selected watershed, the
geometry of the withdrawal points within the watershed, as well as the summary of
consumptive use estimates. The information is displayed in the user interface in
four different ways. First, the elements are highlighted on the map (Fig. 10). This
onscreen display of the selected features is intended to provide the user with visual
confirmation of which watershed and withdrawal points were selected.
Fig. 10 The map user interface showing the highlighted watershed and withdrawal points as
detected from the user’s mouse click (Sources: watersheds—authors; map tiles and data—Stamen
Design and OpenStreetMap)
Interactive Geospatial Analysis Tool for Estimating Watershed-Scale. . .
163
elements stored in the spatial database.
A person utilizes the tool by clicking on a location of interest, such as a
watershed with a potential future withdrawal, to obtain spatial and tabular outputs.
When the user initiates the process by clicking in a watershed on the mapping
interface, a series of scripts are run to perform two major tasks. In the first task, the
system must correctly identify the watershed within which the user has clicked.
This is accomplished through a series of actions that select the smallest nested
watershed under the clicked point and the associated unique identification number.
The second task performed after a user clicks on the map is to return summary
information to the user interface about withdrawal and consumptive use within the
watershed. Using the unique ID of the selected watershed determined from the first
task, a series of additional JavaScript functions, Java Server Page scripts, and
Structured Query Language (SQL) statements are built and sent to the spatial
database to perform a spatial query of the withdrawal points contained within the
selected watershed and calculate the summary information. The spatial database
responds to these queries by returning the geometry of the selected watershed, the
geometry of the withdrawal points within the watershed, as well as the summary of
consumptive use estimates. The information is displayed in the user interface in
four different ways. First, the elements are highlighted on the map (Fig. 10). This
onscreen display of the selected features is intended to provide the user with visual
confirmation of which watershed and withdrawal points were selected.
Fig. 10 The map user interface showing the highlighted watershed and withdrawal points as
detected from the user’s mouse click (Sources: watersheds—authors; map tiles and data—Stamen
Design and OpenStreetMap)
Interactive Geospatial Analysis Tool for Estimating Watershed-Scale. . .
163