Systems and Components – A Process for Developing the Total Water Budget Handbook for Water Budget Development - With or Without Models CWEMF 2019 Annual Meeting April 22, 2019 PRESENTER Todd Hillaire (DWR) COLLABORATORS Abdul Khan (DWR) Paul Shipman (DWR) Saquib Najmus (Woodard & Curran) Frank Qian (Woodard & Curran)

Presentation Outline Total water budget and water budget zone Systems and components Water Budget Accounting Template Handbook organization using systems and components Water budget components – definitions, methods, and data

The Total Water Budget and Water Budget Zone The total water budget is a comprehensive accounting of all inflows to and outflows from the three interrelated and interacting systems in a water budget zone: Land system. Surface water system. Groundwater system. A water budget zone represents any user-defined water management area, such as a watershed, groundwater basin, water district, groundwater sustainability agency (GSA), or other geographical area.

Total Water Budget Schematic Land System Surface Water System Groundwater System

Water Accounting Template – The Total Water Budget

Systems and Components Systems organize a highly complex water budget schematic into manageable units of analysis Represent all inflows, all outflows, and change in storage for each system Check for mass balance error at the system level Systems illustrate flow interactions not captured in a total water budget Inflows and outflows across a system boundary Systems illustrate the internal water flow associated with management. Applied Water - identifies how much water is used for Ag, Urban, and Managed Wetlands but is only an internal flow component but is not a mass balance term Reuse and recycled water – identifies water management actions but is not a mass balance term

Handbook Organization The Handbook organizes components by system – Land, Surface Water, and Groundwater – for ease of analysis. The Handbook provides context, outlines a range of methods, identifies potential data sources, and provides examples by system Individual component calculations are key for modeling and non-modeling approaches. Models need input based on component calculations, such as urban applied water. The Handbook systematically organizes systems and components to roll-up water balances.

Land System - Overview The land system is the portion of the water budget zone that includes the land surface and the unsaturated zone that extends vertically to the top of the groundwater system (i.e., water table).

Land System – Organization by Water Use Sectors Managed land uses Agricultural lands Urban areas, including large landscape and industrial Managed wetlands Native and riparian lands

Land System – Components Precipitation Evapotranspiration Applied Water – agriculture, urban, managed wetlands Surface Water Delivery Groundwater Extraction Applied Water Reuse And Recycled Water Recycled Water Export Runoff Return Flow Change In Land System Storage Note Recharge of Applied Water & Precipitation included in Groundwater System

Water Accounting Template – Land System

Land System Water Budget – Urban Example Inflows = Precipitation + Surface Water Delivery + Groundwater Extraction + Stored Water Extraction Outflows = ET of Precipitation + Recharge of Precipitation + Runoff from Precipitation + ETAW (Landscape) + Recharge of Applied Water + Return Flow of Outdoor Water Use + Return Flow of Indoor Water Use + Managed Aquifer Recharge + Recycled Water Export Change in Land System Storage for Urban Areas = Inflows – Outflows

Urban Applied Water Account for all components of water routing

Agricultural Applied Water Account for all components of water routing

Agricultural Applied Water Account for the sources of supply Account for the components of applied water Similar for managed wetlands – accounts for habitat vegetation and ponding

Estimating Agricultural Applied Water Using the Handbook – An Example Process Defined – “Volume of water applied on agricultural land from all sources of water to meet on-farm crop irrigation requirements.” Context – it is a function of the water management goals and methods used to irrigate a crop and may be unique to each area. Calculation – Agricultural Applied Water = (Crop ET – Effective Precipitation) / Irrigation Efficiency Applied water adjustments - irrigation efficiency, on-farm managed aquifer recharge, shallow groundwater uptake.

Methods for Estimating Agricultural Applied Water Obtain available water delivery data. Use available technical reports and existing numerical models. Estimate applied water volumes (2 approaches) Water-duty based approach Crop ET approach Includes practical steps added to estimate supply by source, recharge, return flow in relation to applied water

Crop ET Approach – Steps to Estimate Applied Water and More Calculate Crop ET Requirements Calculate Precipitation Volume for the Agricultural Area Calculate Runoff Volume Calculate ET of Precipitation Calculate ET of Applied Water Estimate Applied Water using Irrigation Efficiency Calculate Volume of Applied Water Calculate Volume of Groundwater Extraction Calculate Volume of Applied Water Reuse Calculate Volume of Surface Water Delivery Calculate Volume of Irrigation Recharge Calculate Volume of Irrigation Return Flow Practical steps added to estimate supply by source, recharge, return flow

Change in Land System Storage “Net change in the volume of water stored within the land system, which includes ponded water on the land surface (not including streams, lakes, and conveyance facilities) and soil moisture within the unsaturated zone, which includes the root zone.” Inflow to the Land System – Outflow from the Land System = Change in Unsaturated Zone Storage + Change in Ponded Water + Change in Rootzone Storage Methods Use published reports and numerical models Estimate using inflow and outflow balance Use ponded area, depth, and duration to estimate change in ponded water storage Use water use models to determine change in soil moisture storage Estimate change in unsaturated zone storage as a water balance Assessing mass balance error - unrealistic given lack of direct measurements

Surface Water System - Overview The surface water system is the portion of the water budget zone that includes rivers and streams, conveyance facilities and diversion ditches, and lakes and reservoirs that are part of the water supply system for meeting agricultural, urban, and managed wetlands applied water demands.

Surface Water System Organization - Overview Stream Inflow And Outflow Surface Water Diversion Stream Evaporation Conveyance Evaporation Conveyance Seepage Imported Water & Surface Water Export Stream-Lake Interaction Lake Evaporation Change In Surface Water Storage Note Stream-Groundwater Interaction included in Groundwater System

Water Accounting Template – Surface Water System

Stream Inflow And Outflow – Estimating the Components Methods Obtain available streamflow data. Estimate from available streamflow data. Estimate streamflow using drainage area ratio method. Estimate streamflow using rainfall-runoff model Data Sources in component subsection USGS Surface-Water Data for California USGS publications: Water-Resources Investigations Reports , Scientific Investigations Reports DWR California Data Exchange Center (CDEC) DWR Water Data Library Local agency records, including flood control districts or entities managing storm water SWRCB Irrigated Lands Regulatory Program Input/output files of numerical models (e.g. rainfall-runoff model). Data Resources Directory

Groundwater System - Overview The groundwater system is the portion of the water budget zone that extends vertically from the base of the unsaturated zone (water table) to the bottom of the basin within the water budget zone; it can include one or more principal aquifers and represents the physical extent of the water budget zone used to quantify the volume of groundwater stored.

Water Accounting Template – Groundwater System

Groundwater System - Components Recharge Of Applied Water And Precipitation Subsurface Inflow And Outflow Stream-groundwater Interaction Lake-groundwater Interaction Managed Aquifer Recharge Stored Water Extraction Groundwater Export Stored Water Export Change In Groundwater Storage Water Release Caused By Land Subsidence

Defining Recharge and Store Water Terms Recharge Of Applied Water And Precipitation focuses on the term “Recharge” instead of “Deep Percolation” to better define destination of water Managed Aquifer Recharge is part of defined recharge and water banking programs through spreading basins, injection wells, and other means. Stored Water Extraction – groundwater pumped from the underlying aquifer(s) through a defined recharge and extraction program for use within the water budget zone. Stored Water Export - groundwater pumped from the underlying aquifer(s) through a defined recharge and extraction program for use outside the water budget zone.

Change In Groundwater Storage “Net change in the volume of groundwater stored within the underlying aquifer of the water budget zone.” Change in Groundwater Storage = Inflow to Aquifer (Recharge) – Outflow from Aquifer (Discharge) Can estimated using direct measurements (groundwater levels) or using indirect measurements (remote sensing) coupled with modeling tools Evaluate mass balance error: Mass Balance Error = Inflow to Aquifer – Outflow from Aquifer – Change in Groundwater Storage (measured)

Water Release Caused By Land Subsidence “Volume of water released to an aquifer on a one-time basis as a result of land subsidence, which is caused by the inelastic consolidation of porous fine-grained material.” Methods: Obtain available technical reports and modeling studies. Estimate using model results and groundwater level data.

Key Takeaways The Handbook provides a systematic process for: Estimating water budget components Aggregating components for system and total water budget balances Estimating change in storage for each system Evaluating mass balance error Systems help to organize water budget development and provide water budget checks Handbook organizes systems and components to promote a sequential pathway for water budget development See “Case Study: Non-Modeling Approach” presentation Handbook provides component definitions, context, methods, data sources (including the Data Resources Directory), and examples

Questions?