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Water Planning Projections

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An Overview

The Nevada Irrigation District presented updated Water Planning Projections to its Board of Directors on Wednesday, August 26, 2020. Here you will find summary information as well as the Technical Memorandums (TMs) associated with each study.

The Water Planning Projections consists of three studies that analyze the hydrology, water supply and water demand that help NID determine if its water storage and delivery system will provide sufficient water to meet customer demands over time and under variable conditions.

The Water Planning Projections are used to prepare a number of planning reports such as the Urban Water Management Plan and the Agricultural Management Plan (see description below) required to be updated and submitted to the State of California every five years. The Water Planning Projections is also used to prepare the District’s Plan for Water, formerly called a Raw Water Master Plan (see descriptions below), and is considered when making decisions about capital improvements to its water storage and delivery system.

The need to update NID’s Water Planning Projections is driven by a series of requirements and assumptions, including the new Yuba-Bear System Federal Energy Regulatory Commission (FERC) regulatory requirements, state-derived climate change data, and the state-mandated planning requirements. Together, these requirements and assumptions constitute significantly new planning assumptions and drive the need to update and revise NID’s Water Planning Projections when necessary.

About Water Planning Projections

Water Planning Projections is a term used to reference the combination of three studies that are used for District planning; a Hydrologic Analysis, Water Supply Analysis, and a Water Demand Projection (see descriptions below).

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About the Hydrologic Analysis

The goal of the Hydrologic Analysis is to understand a range of outcomes based on various greenhouse gas emissions reduction scenarios and to determine the unimpaired flow, the amount of water available in the natural watershed without influence (i.e., regulation of stream flow by man-made structures such as dams or diversions). The State of California anticipates conditions under climate change to include warmer temperatures; rising sea levels; declining snowpack; more intense precipitation events; more droughts; and more area burned by wildfire. These factors, among others, will ultimately impact the amount of water available in a watershed in any given year.

The result of this analysis is the unimpaired runoff in NID’s watersheds under various climate change scenarios. This information is needed to compile the Water Supply Analysis (see below).

Additional Hydrologic Detail as Presented at August 26 Board of Directors Meeting.

To read the Hydrologic Analysis Technical Memorandum click here.

To review the Hydrologic Analysis TM Appendices  click here


About the Water Supply Analysis

The Water Supply Analysis uses the unimpaired runoff results from the Hydrologic Analysis to determine available water supply to NID over time and under certain conditions. NID’s four main sources of water are: natural snowmelt and resulting runoff, reservoir storage carryover (unused from prior year), contract water purchases, and recycled water released by treatment plants and later diverted to NID irrigation canals.

The Water Supply Analysis has been updated to consider the impact of drought, climate change, contract purchases, and new FERC license conditions for environmental flows on its water supply system. An additional carryover storage model is also used to determine what NID reservoir storage carryover will be from year to year.

The result of this analysis is the amount of water available to NID during average and wet years, as well as during a 5-year drought scenario. It is the amount available to meet regulatory required environmental flows, customer demand for raw or irrigation water, customer demand for treated or drinking water, municipal purchases and to cover system losses.

Additional Supply Detail

Five Year Drought Alternative Analysis – as requested at Technical Clarification Meeting and for UWMP

To read the Water Supply Analysis Technical Memorandum click here.


About the Water Demand Projection

The Water Demand Projection looks at future water demands on NID’s water storage and delivery system. The five components of total water demand are: the demand for raw or irrigation water, the demand for treated or drinking water, required environmental flows, system losses, and municipal purchases. It is important to note that 85 percent of NID’s water deliveries are raw water used for irrigation purposes.

Calculating demand is a very simple process of multiplying the projected water demand factor by the number of customers or parcel size. While the multiplication is easy, numerous assumptions are made including economic and demographic assumptions, regulatory and legal impacts, operational assumptions, and others that effectively assume a state of the NID community in 50 years.

The result of this projection is a range of future customer demands for treated and raw water.

Additional Demand Factor Detail as Presented at August Board Meeting

Updated Flows by Service Area Charts

To read the Water Demand Projection Technical Memorandum click here

Responses to Questions Provided by Public with Answers

Water Planning Projections PowerPoint From Aug 26 Board of Directors Meeting

VIDEO: September 24, 2020 – Water Planning Projections Technical Clarification Meeting  – Scroll to bottom

Other Helpful Information

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