Prior Appropriation Water Rights - An Excel Based Lab

Author: Alejandro N. Flores

Spring 2021

Purpose

The purpose of this module and quantitative lab is to acquaint students with Prior Appropriation water rights (the prevailing water rights legal framework in the Western US) by having them implement water withdrawals from a fictional river in accordance with the seniority of each water right. The module was originally developed for a sophomore-level class at Boise State University, GEOS 212: Water in the West. In the lab, as designed, students explore three scenarios. Scenario 1 involves transforming the water rights into daily diversions from a fictional river into daily withdrawals based on the date and diversion rate. In this scenario river flow is always sufficient to meet all needs, but students are prompted to plot the discharge in the river downstream of/after all withdrawls to examine the impact of diversions on river flow. In Scenario 2, students are confronted with a hydrograph that might be more typical of a warming climate with an earlier and sharper peak flow, and lower base flow. In this scenario, students must curtail water users based on the seniority of the water rights. Scenario 3 provides students with a simple reservoir into which they can divert water when flow is sufficiently high to use as storage when flows recede and become insufficient for demand (the sum of all active water rights claims). In this scenario, there is sufficient volume of water to meet all demands, but students must schedule the beginning and ending of reservoir filling and the beginning of water withdrawl from storage to meet downstream demand. For simplicity: (1) the reservoir fill and spill rates are the same (10,000 cfs), (2) there is a fixed reservoir capacity shown to the students, (3) once the student starts using stored water they cannot "close the gates" of releases. In scenario 3, they also must maintain a minimum streamflow of 1,500 cfs for in-stream habitat purposes.

Learning Objectives

By the end of this module, studens will be able to: List some consumptive uses of water Articulate the principle of Prior Appropriation In the context of water rights, describe what curtailment is Translate water rights information into a schedule of diversions Simulate the effect of water withdrawals on a streamflow hydrograph Develop a report as a member of a team

Requirements and Dependencies

Students should have some introduction to water rights and prior appropriation, in particular. Exissting web resources used in GEOS 212 in Spring 2021 are linked below. The lab also requires that students be familiar with and comfortable with mass balance as they will be required to correctly record the equation to compute flow in the Dumont River after all diversions and, for scenario 3, reservoir withdrawls and releases. The lab assumes that students have access to a computer with internet access and Microsoft Excel. The lab may work in Google Sheets or other open-source spreadsheet software packages, but has not been tested.

Materials Included

This module consists of the following materials:

• This README.md
• Microsoft Excel spreadsheet to create streamflow hydrographs as input (Water Rights Lab Input Hydrographs (Instructor Use Only).xlsx)
• Microsoft Excel spreadsheet template in which students carry out activities (Water Rights Lab Student Workbook.xlsx)
• Microsoft Word Document containing background and exploratory questions for the students to address throughout the exercise (Water Rights Lab Packet.docx)
• A 10-question pre-review quiz as a zip file that can be imported to Blackboard, Canvas, or other learning management systems (Water Rights Quiz QTI package.zip)

Web Resources

• A video by Colorado Assistant Attorney General Kate Ryan about prior appropriation: https://www.youtube.com/watch?v=HABiWSskaAY
• A video about the Snake River Basin Adjudication: https://youtu.be/EypZIZUyZkM
• A pampmlet from the Idaho Department of Water Resources with some key water rights terminology for Idaho: https://idwr.idaho.gov/files/water-rights/water-rights-brochure.pdf

Instructions to the Instructor

The streamflow hydrographs were created using a scaled lognormal distribution in Microsoft Excel. These hydrographs can easily be modified to evaluate alternate scenarios by, for instance, shifting the timing of the peak, the baseflow, or the scaling of the lognormal distribution. In this workbook there is a spreadsheet for each scenario. New scenarios could be added by copying an existing sheet as a template. Note, if you also change the water rights information, you will want to copy and paste the summed daily diversions to evaluate the extent to which the student will have to curtail users or use the reservoir.

Key

For the key to this lab, please email: lejoflores@boisestate.edu

Assumptions and Limitations

• The lab works most easily when the student implements water rights as binary – they are either off or on. What this means practically is that when it is time to curtail a user, their diversion goes to 0.
• The lab is essentially aspatial, making no assumptions about where the water is withdrawn. In scenario 3 the storage reservoir can be thought of as in parallel to the river system, with a single diversion into the reservoir and a single reservoir outlet.
• It is assumed there are no return flows to the river. All water withdrawn from the Dumont River is lost from the system.
• For simplicity, the reservoir is set to a constrained fill and spill rate of 10,000 cfs and a fixed reservoir volume.