1. Francisco Flores-López, Ph.D. California Department of Water Resources
Innovative Studies and Tools to Support Using Flood Water for Management Aquifer
Flood MAR Recharge Schedule and Allocation Modeled through IDC-GRAT
Francisco Flores-López, Ph.D.
California Department of Water Resources

2. Flood-MAR Models Integration IWFM Demand Calculator (IDC) Description
CALIFORNIA DEPARTMENT OF WATER RESOURCES
Presentation Agenda
Flood-MAR Models Integration
IWFM Demand Calculator (IDC) Description
Groundwater Recharge Assessment Tool (GRAT) Description
IDC – GRAT Recharge Schedule and Allocation

3. Models Integration for the Merced Flood-MAR Study
Sac-SMA
Hydrologic Model
CalLite
System Model
Res-Sim (MIDH2O)
Reservoir Model
HEC-RAS (MIDH2O)
Hydraulic Models
HEC-FIA
Flood Risk Models
IDC
Root Zone Model
FM2Sim
Groundwater Model
GRAT
Recharge Optimization
HEC-HMS (MIDH2O)
Hydraulic Model
IDC
Maximum flood water application & frequency based on crop and soil types
IDC
Root Zone Model
GRAT
Flood water allocation based on a crop compatibility calendar
GRAT
Recharge Optimization
1. Model integration was described by colleague David Arrate in the previous presentation
2. (a) This presentation focuses on two highlighted models, the IDC root zone model and the recharge optimization model GRAT
(b) These two models are going to be described in detail during the following slides, the input data needed to run the models, the expected outputs and how these outputs feed the reservoir model (ResSim) and the groundwater model (FM2Sim)
3. The purpose of the IDC model is to determine the maximum amount of flood water and intervals between flooding events for the different crop and soil types identified in the study area. This maximum amount of flood water can be described as:
(a) Amount of water needed to saturate the root zone profile and also to have a specific ponded depth for a single flooding event
(b) Amount of water needed to re-apply in order to keep the ponded depth during subsequent days for the numbers of days that we want to keep the field flooded.
(‘c) After flood water application stops, the return interval or number of days that the it would take the soil to drain down water so crops are not damaged by excess of water or anaerobic conditions
(e) The purpose of the GRAT model is to determine a tailored crop compatibility calendar for the Merced ID. This tailored crop compatibility calendar is going to specify the maximum daily water application amount and frequency per crop and soil type. The crop compatibility calendar will include the crop-specific field cultural operation practices among other factors later described in this presentation.
(f) GRAT will include daily precipitation in calculating the amount of water that can be applied per field in each climate run scenario.
(g) GRAT’s outputs will be used by the reservoir simulation and ground water models and it will be explained in details during next presentation.

4. Flood-MAR Models Integration IWFM Demand Calculator (IDC) Description
CALIFORNIA DEPARTMENT OF WATER RESOURCES
Presentation Agenda
Flood-MAR Models Integration
IWFM Demand Calculator (IDC) Description
Groundwater Recharge Assessment Tool (GRAT) Description
IDC – GRAT Recharge Schedule and Allocation Integration

5. IWFM Demand Calculator - IDC
Stand-alone root zone component of IWFM (v2015)
Calculates water demands and routes water
Agricultural water demands
Climate data
Crop type and crop acreage
Soil properties
Irrigation methods
Spatially distributed model of:
Land-use (ponded and non-ponded)
Climate
Soil and farm management properties
Budget outputs for individual crops
This slide shows the schematic of the modular component that IDC focuses on, the land surface and root zone.
IDC is a grid-cells spatial-distributed model with specific land-use types, soil and farm management practices and climate in each grid-cell.
Grid-cells can be defined as non-ponded and ponded cells based on land use types and needs
IDC does a soil water content budget for the root zone for each grid-cell based on land surface, water demands, water supplies, and root zone fluxes
Simulation of processes are done for each grid cell and land-use type
Source: E. C. Dogrul, DWR IDC-2015

6. IWFM Demand Calculator - IDC
Soil Moisture Routing
P: Precipitation
Rp: Direct Runoff
Aw: Applied Water
Rf: Net Return Flow
U: Re-use of Return Flow
G: Generic Moisture Inflow
Dr: Drainage of Rice and Refuge Ponds
D: Deep Percolation
ET: Evapotranspiration
This schematic describes the different processes that are simulated by IDC in the root zone.
Precipitation that falls on the ground surface infiltrates into the soil at a rate dictated by the type of ground cover, physical characteristics of the soil and the moisture that is already available in the soil. The portion of the precipitation that is in excess of the infiltration rate generates a surface runoff.
Infiltration due to precipitation and irrigation replenish the soil moisture in the root zone which is also depleted through plant root uptake for transpiration and additional evaporation from the top layers of the soil.
In IDC , it is assumed that the horizontal movement of the moisture is negligible compared to the vertical movement. Therefore only the flow of the moisture in the vertical direction is addressed. The moisture that leaves the root zone through its bottom boundary is defined as deep percolation.
IDC uses a physically-based approach to compute the flow terms mentioned above and to route the soil moisture through the root zone. For a particular land use type and grid-cell, the conservation equation for the soil moisture discretized in time is showed above quantifying inputs, outputs and changes in storage.
Source: E. C. Dogrul, DWR IDC-2015

7. Flood-MAR Models Integration IWFM Demand Calculator (IDC) Description
CALIFORNIA DEPARTMENT OF WATER RESOURCES
Presentation Agenda
Flood-MAR Models Integration
IWFM Demand Calculator (IDC) Description
Groundwater Recharge Assessment Tool (GRAT) Description
IDC – GRAT Recharge Schedule and Allocation Integration

8. Groundwater Recharge Assessment Tool - GRAT
Groundwater Recharge Assessment Tool (GRAT) has been developed by Sustainable Conservation and the Earth Genome
GRAT is a decision support tool that evaluates where, when, and how much water can be applied based on best available data and hydrologic, agronomic and geologic science.
The tool enables users to identify the most cost effective options for groundwater recharge through a crop compatibility calendar.
For the Merced Flood-MAR Study, GRAT will be tailored for the project’s needs. One change to be done is the time-step: from weekly to daily.
Another example of insufficient data:
Research exists on flood effects on crops on heavy soils
UC Davis has been developing data on alfalfa and almonds for winter period
Sustainable Conservation and Bachand and Associates are collecting data on extended season recharge on 4 crops
Growers and agronomists have been applying excess water for research so we gathered their experience for first draft of calendar.
Continue to update calendar as new science is developed.
Project with DWR using IDC will allow consideration of different soil type drainage rates to establish better estimates of recharge return frequency to avoid saturation of root zone.
Where is recharge best done? When?
How much water can we apply (capacity of crops to receive water in excess of crop demand)?
What would it cost?
Best available data based on farmer and field agronomist experience
Available for grapes, alfalfa, walnuts, almonds, pistachios
Slide Source:

9. On-Farm and Fallow Recharge
Groundwater Recharge Assessment Tool - GRAT
Conveyance
Water Available for Recharge
Conveyance infrastructure
Delivery capacity to fields
Surface water availability
Excess flood flows
Water rights
Merced Flood-MAR
Study
Schematic of GRAT logic
The water available for recharge in GRAT is defined by the surface water availability, the excess flood water and/or water rights.
For the Merced Flood-MAR study, the study itself will define the water available for recharge
GRAT optimizes application of available water across fields, based on site characteristics (conveyance, soil and geologic recharge suitability, crop compatibility calendar) and timing of water availability.
The groundwater recharge method is defined by user
GRAT will estimate the total cost of groundwater recharge and in this study, the increase in groundwater recharge will be estimated by the groundwater model
Site Suitability
Recharge suitability: slope, soil type, clay layers, underlying geology, depth to groundwater
Crop and land use suitability
On-Farm and Fallow Recharge
Infiltration-percolation potential
(crop compatibility calendar)
Percolation rate of existing dedicated recharge basins
Dedicated Basins
Recharge Benefit/Cost Analysis
Slide Source:
Relative cost per acre foot ($/acre foot)
Increased groundwater recharge
Increased groundwater recharge (FM2Sim)

10. Flood-MAR Models Integration IWFM Demand Calculator (IDC) Description
CALIFORNIA DEPARTMENT OF WATER RESOURCES
Presentation Agenda
Flood-MAR Models Integration
IWFM Demand Calculator (IDC) Description
Groundwater Recharge Assessment Tool (GRAT) Description
IDC – GRAT Recharge Schedule and Allocation Integration

11. GRAT Recharge Optimization Model
IDC - GRAT Integration
IDC Root Zone Model
Daily Input => Daily Output
Maximum Flood Water Application & Frequency
Crop types (ET, ponding depth, number of days under flooded, interval between flooding events)
Soil properties (Ksat and other physical soil parameters)
Recharge Suitability (SAGBI Index)
Outcome
Maximum Flood Water per unit area (inches)
GRAT Recharge Optimization Model
Daily Input => Daily Output
Flood Water Allocation
Areas available (e.g. crop compatibility calendar, Land IQ Suitability Index, conveyance, etc.)
Flood Water Demand (Max Flood Water * Available areas)
Location of fields to be flooded (distribution consistent with FM2Sim)
Outcome
Recharge Locations
Flood Water Deliveries
Estimated Total Cost
The IDC model calculates the maximum flood water to apply and the frequency based on crop type, soil physical properties such as Ksat and the recharge suitability index (SAGBI index)
The IDC outcome (the maximum Flood water per unit area for a single flooding event) is transferred to the Groundwater Recharge Assessment Tool per crop and per soil type
GRAT will use these maximum flood water and frequency to allocate water based on available crop areas taking into account the crop compatibility calendar, land IQ suitability index, conveyance and infrastructure, etc.
The flood water demand will be determine by GRAT as the product of max flood water and available areas for recharge
GRAT will determine the location of individual fields to be flooded and how much to apply and when
GRAT results will be the recharge location, flood water deliveries, and estimated total cost for groundwater recharge

12. 3 different Soil Types (SAGBI Index)
IDC Conceptual Model
Up to 13 different Crop/Land Use Types
Since we are going to use the Land IQ database for the Merced ID, we have identified a set of 7 different potential perennial crops that we can flood and annual crop lands that can potentially be flooded as well.
We have developed a conceptual or dummy IDC model where each grid-cell is specific for crop/land type and soil type.
We are targeting only the top three SAGBI Suitability Index (Excellent, Good and Moderately Good)
The corresponding soil parameters for each individual soil texture type are shown
3 different Soil Types (SAGBI Index)
1-Acre Grid
Dummy Model

13. IDC Conceptual Model Results
Crop: Almonds
ET: Potential ET
Root Depth: 6 feet
Flooding Duration: 5 days (Dec 01 – 05)
Max Pond Depth: 3 inches
SAGBI Index: Moderately Good
Soil Texture Type: Sandy Loam
Soil Depth: 6 feet
Ksat: 2 feet/day
Wilting Point: 8.9 (% Vol.)
Field Capacity: 20.8% (% Vol.)
Total Porosity: 41.2% (% Vol.)
No Precipitation
We have developed conceptual IDC models to determine the maximum Flood-MAR demands.
This conceptual model is crop type and soil type specific with a daily time-step
The current slide shows the applied water, percolation, and water storage for a 5 days ponded event and 3 inches ponded depth starting on December 1st
The crop simulated here is Almonds, and the soil type is Sandy Loam with a Moderately Good SAGBI Index and corresponding soil physical parameters that characterize this soil type
The model does not have irrigation or precipitation so we determine the maximum amount of water needed to saturate the soil and get the desired ponded depth

14. IDC Conceptual Model Results
Day
Applied Water (in) 1
38.5 2
24.0 3 4 5
Next flooding event: > 5 days
5-days Flooding
Taking a close look at the graph, we can define the amount of water needed to saturate the soil profile, have 3 inches pond and provide the water that percolates during day 1
The crop is flooded for 5 consecutives days and on day 5, applied water stops.
For this type of soil (Sandy Loam) it takes about 2 days for the water content to drain out to ¾ od saturation, 5 days to reach out half way between saturation and field capacity, 18 days to reach ¼ saturation and about 46 days field capacity over the 6 feet depth soil profile.
The interval between day 2 and day 46 after we stop adding water is the potential window for re-applying flood water that is define based on crop type, farmer’s desire to re-apply water or take the risk, management practices, and even availability of water for Flood-MAR purposes.
This information will be used by the GRAT model specifically in the Crop Compatibility Calendar
2 days return interval (3/4 saturation)
3 in
5 days return interval (1/2 saturation)
18 days return interval (1/4 saturation
46 days (field capacity)
Potential return interval between flooding

15. Groundwater Recharge Assessment Tool - GRAT
Crop Compatibility Calendar
The crop compatibility calendar informs how much water can be applied throughout a crop cycle
The crop compatibility calendar uses the maximum flood water for recharge calculated by IDC, takes into account Etc and Precipitation, and determines the total applied water
The crop compatibility calendar considers the crop management operations or practices to avoid flooding during these critical days
And finally determines the when and how much water can be applied. For the Merced Flood MAR study the crop compatibility calendar will be on a daily time-step
This definition and functionality allows the tool user to specify a more complete “budget” for groundwater overdraft and recharge. Options for toggling on/off different recharge types (e.g. dedicated recharge basins) allow the GSA to test scenarios that determine best portfolio of recharge options.
Slide Source:

16. Groundwater Recharge Assessment Tool - GRAT
Recharge Type, Site Selection, and Water Allocation
Optimizes application of available water
Based on
With the information provided by IDC, GRAT will allocate that maximum Flood-MAR demands based on user criteria or needs
User determine the selection of recharge type and crop type for on-farm recharge
Then GRAT optimizes the application of available water based on:
1. Site Characteristics
i) Conveyance / Water Access: Proximity and size of existing water conveyance for any field unit
ii) Soil and geologic recharge suitability: this determines the ability of water to percolate down to the first encountered aquifer per SAGBI/ LandIQ index
iii) Crop Compatibility Calendar: determines the amount of water that can be applied based on the crop compatibility calendars
2. Timing of water availability
1. Site Characteristics
i) Conveyance / Water Access
ii) Soil and geologic recharge suitability
iii) Crop Compatibility Calendar
2. Timing of Water Availability
Slide Source:

17. Groundwater Recharge Assessment Tool - GRAT
Results: Acreage Used by Crop, Remaining Acreage Potential, On-Farm Recharge, and Estimated Costs
This slide shows part of the GRAT results. As an example GRAT will provide the total acreage used for on-farm recharge by crops
Reports also indicate how many acres of each crop were used (blue) and how many acres are still available (black) if the Merced ID can incentivize additional participation
GRAT will report the recharge volume by crop type and the corresponding estimated total cost for recharge
Slide Source:

18. GRAT Recharge Optimization Model
IDC - GRAT Integration
IDC Root Zone Model
Daily Input => Daily Output
Maximum Flood Water Application & Frequency
Crop types (ET, ponding depth, number of days under flooded, interval between flooding events)
Soil properties (Ksat and other physical soil parameters)
Recharge Suitability (SAGBI Index)
Outcome
Maximum Flood Water per unit area (inches)
GRAT Recharge Optimization Model
Daily Input => Daily Output
Flood Water Allocation
Areas available (e.g. crop compatibility calendar, Land IQ Suitability Index, conveyance, etc.)
Flood Water Demand (Max Flood Water * Available areas)
Location of fields to be flooded (distribution consistent with FM2Sim)
Outcome
Recharge Locations
Flood Water Deliveries
Estimated Total Cost
GRAT’s results will be transferred to the reservoir model to release the allocated flood water based on a “calendar of releases”
GRAT will provide flood water deliveries and recharge location to the groundwater model
GRAT will estimate total costs of flood water deliveries
The details of the reservoir simulation model will be describe in the following presentation.
Res-Sim (MIDH2O)
Reservoir Model
FM2Sim
Groundwater Model

19. Flood MAR Recharge Schedule and Allocation Modeled through IDC-GRAT
CALIFORNIA DEPARTMENT OF WATER RESOURCES
Innovative Studies and Tools to Support Using Flood Water for Management Aquifer California Water & Environment Modeling Forum 2019 Annual Meeting
Flood MAR Recharge Schedule and Allocation Modeled through IDC-GRAT
The Flood-MAR Team
David Arrate (DWR)
Francisco Flores-López (DWR)
Daniel Mountjoy (Sustainable Conservation)
Alex Vdovichenko (DWR)
James Wieking (DWR)
Glen Low (Earth Genome)
Shem Stygar (DWR)
Jennifer Marr (DWR)
Devon Lake (Earth Genome)
Romain Maendly (DWR)
Ajay Goyal (DWR)
Liz DaBramo (Woodard & Curran)
Wyatt Arnold (DWR)
Lee Bergfeld (MBK)
Sercan Ceyhan (Woodard & Curran)
Clark Churchill (DWR)
Wesley Walker (MBK)
Ali Taghavi (Woodard & Curran)