BMP treatment technologies, monitoring needs, and knowledge gaps: status of the knowledge and relevance within the Tahoe Basin

This Technical memorandum fulfills Task 2 for Agreement 03-495 between El Dorado County and the Office of Water Programs at California State University Sacramento and their co-authors, Bachand & Associates and the University of California Tahoe Research Group: 1) a review of current stormwater treatment Best Management Practices (BMP) in the Tahoe Basin and their potential effectiveness in removing fine particles and reducing nutrient concentrations; 2) an assessment of the potential for improving the performance of different types of existing BMPs through retrofitting or better maintenance practices; 3) a review of additional promising treatment technologies not currently in use in the Tahoe Basin; and 4) a list of recommendations to help address the knowledge gaps in BMP design and performance. ... (PDF contains 67 pages

Chemical Treatment Methods Pilot (CTMP) System for Treatment of Urban Runoff – Phase I. Feasibility and Design

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2017 OFR demonstration site monitoring and analyses: Effects on soil hydrology and salinity, and potential implications on soil oxygen

On-farm recharge (OFR) is a practice that uses surface water to alleviate demand on and replenish groundwater supplies. It can take on two forms: in lieu recharge and direct recharge. In lieu recharge utilizes surface water supplies instead of groundwater to irrigate crops. Direct recharge applies water beyond the needs of the crop and replenishes the groundwater supply. ... The present study examined OFR with grapes, walnuts, and pistachios at six sites in the San Joaquin Valley, plus one additional site from a previous study, also in the San Joaquin Valley. Each site was comprised of a recharge plot that received direct recharge paired with a control plot with the same crop and soil characteristics, but meant to receive in lieu recharge (via the flood system) or drip application with groundwater. At the end of the 2017 recharge demonstration, however, three control plots had also received direct recharge from water applications that exceeded the crop’s water demand. At another site, both control and test plots had only received in lieu recharge due to limited surface water amounts or the host growers’ more conservative volume of water application. ... The present study only covers one season of recharge. Long-term effects of recharge are not described by the present study and will require further monitoring. Further study is needed of the dynamics of soil oxygen during and after recharge events. Similarly, the fate of the water after it infiltrates past the root zone is not always known and the rate at which recharged water will reach an aquifer is seldom known for deep aquifers. A method to predict the fate of water quickly and broadly would be quite helpful in developing an on-farm recharge strategy. The present study does not look at the effects of recharge on soil biological processes, such as microbial respiration and plant oxygen demand. Further study of the recharge tolerance of specific species and rootstocks, as well as the impact on plant disease, is crucial

On-Farm Flood Capture and Recharge (OFFCR) at an Organic Almond Orchard, Recharge Rates and Soil Profile Responses Groundwater Recharge Project, 2016

Groundwater in much of California’s Central Valley (CV) has been critically over-drafted resulting in the implementation of the 2014 Sustainable Groundwater Management Act (SGMA). As Groundwater Sustainability Agencies (GSAs) work to comply with SGMA requirements and timelines, On-Farm Floodwater Capture and Recharge (OFFCR) is being studied to help increase recharge capacity. We implemented an OFFCR test on an organic almond orchard in the CV to assess achievable recharge rates attained through over-irrigation, and potential soil and water quality impacts. Irrigation water was applied via flood irrigation. We developed study sites and installed soil sensors for moisture and salinity monitoring, took post-irrigation deep cores to assess changes in soil and porewater nitrogen and salt concentrations through the vadose zone, and monitored agronomic practices, recharge loading and crop yields. These studies were conducted on three recharge treatments with three replicated stations for each: 1) Control at about 6 inches of flooded water to meet ET as typical for irrigation (Control treatment), 2) Low Flooding of about 12 inches per irrigation application (Mid treatment), and 3) High Flooding of about 24 inches per irrigation application (High treatment)

Feasibility Analysis of South Bay Salt Pond Restoration, San Francisco Estuary, California

228pp. (pdf contains 257 pages

Implications of using On-Farm Flood Flow Capture to recharge groundwater and mitigate flood risks along the Kings River, CA

Two large hydrologic issues face the Kings Basin, severe and chronic overdraft of about 0.16M ac-ft annually, and flood risks along the Kings River and the downstream San Joaquin River. Since 1983, these floods have caused over $1B in damage in today’s dollars. Capturing flood flows of sufficient volume could help address these two pressing issues which are relevant to many regions of the Central Valley and will only be exacerbated with climate change. However, the Kings River has high variability associated with flow magnitudes which suggests that standard engineering approaches and acquisition of sufficient acreage through purchase and easements to capture and recharge flood waters would not be cost effective. An alternative approach investigated in this study, termed On-Farm Flood Flow Capture, involved leveraging large areas of private farmland to capture flood flows for both direct and in lieu recharge. This study investigated the technical and logistical feasibility of best management practices (BMPs) associated with On-Farm Flood Flow Capture. The investigation was conducted near Helm, CA, about 20 miles west of Fresno, CA. The experimental design identified a coordinated plan to determine infiltration rates for different soil series and different crops; develop a water budget for water applied throughout the program and estimate direct and in lieu recharge; provide a preliminary assessment of potential water quality impacts; assess logistical issues associated with implementation; and provide an economic summary of the program. At check locations, we measured average infiltration rates of 4.2 in/d for all fields and noted that infiltration rates decreased asymptotically over time to about 2 – 2.5 in/d. Rates did not differ significantly between the different crops and soils tested, but were found to be about an order of magnitude higher in one field. At a 2.5 in/d infiltration rate, 100 acres are required to infiltrate 10 CFS of captured flood flows. Water quality of applied flood flows from the Kings River had concentrations of COC (constituents of concern; i.e. nitrate, electrical conductivity or EC, phosphate, ammonium, total dissolved solids or TDS) one order of magnitude or more lower than for pumped groundwater at Terranova Ranch and similarly for a broader survey of regional groundwater. Applied flood flows flushed the root zone and upper vadose zone of nitrate and salts, leading to much lower EC and nitrate concentrations to a depth of 8 feet when compared to fields in which more limited flood flows were applied or for which drip irrigation with groundwater was the sole water source. In demonstrating this technology on the farm, approximately 3,100 ac-ft was diverted, primarily from April through mid-July, with about 70% towards in lieu and 30% towards direct recharge. Substantial flood flow volumes were applied to alfalfa, wine grapes and pistachio fields. A subset of those fields, primarily wine grapes and pistachios, were used primarily to demonstrate direct recharge. For those fields about 50 – 75% of water applied was calculated going to direct recharge. Data from the check studies suggests more flood flows could have been applied and infiltrated, effectively driving up the amount of water towards direct recharge. Costs to capture flood flows for in lieu and direct recharge for this project were low compared to recharge costs for other nearby systems and in comparison to irrigating with groundwater. Moreover, the potentially high flood capture capacity of this project suggests significant flood avoidance costs savings to downstream communities along the Kings and San Joaquin Rivers. Our analyses for Terranova Ranch suggest that allocating 25% or more flood flow water towards in lieu recharge and the rest toward direct recharge will result in an economically sustainable recharge approach paid through savings from reduced groundwater pumping. Two important issues need further consideration. First, these practices are likely to leach legacy salts and nitrates from the unsaturated zone into groundwater. We develop a conceptual model of EC movement through the unsaturated zone and estimated through mass balance calculations that approximately 10 kilograms per square meter of salts will be flushed into the groundwater through displacing 12 cubic meters per square meter of unsaturated zone pore water. This flux would increase groundwater salinity but an equivalent amount of water added subsequently is predicted as needed to return to current groundwater salinity levels. All subsequent flood flow capture and recharge is expected to further decrease groundwater salinity levels. Second, the project identified important farm-scale logistical issues including irrigator training; developing cropping plans to integrate farming and recharge activities; upgrading conveyance; and quantifying results. Regional logistical issues also exist related to conveyance, integration with agricultural management, economics, required acreage and Operation and Maintenance (O&M)

On-Farm Flood Flow Capture – addressing flood risks and groundwater overdraft in the Kings Basin, with potential applications throughout the Central Valley

Project fact sheet prepared in cooperation with the USDA Natural Resources Conservation Service and the Kings River Conservation District

Phase II Low Intensity Chemical Dosing (LICD): Development of Management Practices

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McMullin On-Farm Flood Capture and Recharge Project: Hydrologic and Hydraulic Analyses (H&H), final report

Approval of a Hydrologic and Hydraulic Analyses (H&H) by California Department of Water Resources (DWR) is a pre-requisite for projects being funded through DWR’s Flood Corridor Program. The H&H needs to show early in the project schedule in analysis acceptable to DWR that the project will produce the anticipated flood risk reduction benefits. A Benefit:Cost (B/C) ratio provides a metric for comparing benefits from a project in relation to DWR costs for the project. In our analysis, we calculated a B/C of 1.86 for Phase 1, the diversion of 150 cubic feet per second (cfs) from the Kings River onto the project during flood flow conditions between December and May, and of 1.98 for Phase 2/3, the diversion of 500 cfs from the Kings River onto the project during the same conditions. We provide background on the project and the area that will be affected by the project (the study area), summarize our methods, and present our findings. Two large hydrologic issues face the Kings Basin: severe and chronic overdraft of about 0.16M ac-ft annually, and flood risks along the Kings River and the downstream San Joaquin River. Since 1983, downstream communities along the Kings and San Joaquin Rivers have suffered over $1B in flood damages (2013$). To help mitigate these two issues, this project proposes diverting and capturing Kings River floodwater at the James Bypass onto agricultural lands adjacent to the Kings River for conjunctive use purposes (e.g. recharge, in lieu recharge, irrigation). This project is planned in three phases: Phase 1 (Ph1) will divert 150 cubic feet per second (cfs) onto agricultural fields from December through May and 100 cfs from June through September. Fifty-five hundred acres are planned for enrollment in Ph1 with 375 acres under flood easements; 1,125 acres managed under dual purpose of accepting flood flows and being managed for farming; and the remaining acreage receiving flood flows when available for in lieu recharge. Phases 2 and 3 (Ph 2/3) together will expand enrollment to 16,000 acres with expected equivalent ratios for flood easements, dual purpose and farming. Ph2/3 is planned to have a 500 cfs flood diversion and capture capacity. We assessed hydrologic and hydraulics conditions and economics for these planned phases following the scope of work defined in Task Order 1 between Kings River Conservation District (KRCD) and Tetra Tech

Technical report: Modeling nitrate leaching risk from specialty crop fields during on-farm managed floodwater recharge in the Kings Groundwater Basin and the potential for its management

This project has focused on better understanding the potential impact of On-Farm Flood Capture and Recharge (OFFCR) on groundwater quality pertaining to salts and nitrate and on assessing potential management opportunities. To achieve these goals, we used a combination of field and modeling studies. For the field study, soil cores were taken to a depth of 30 feet in replicate across fields with three different specialty crops identified as important to the San Joaquin Valley (tomatoes, almonds, vineyards) and with potential suitability for OFFCR. A prime goal of the field study was to provide data for parameterizing two models developed to assess nitrate, salt and water transport through the vadose zone, prior to percolating into the groundwater aquifer. However, the field study also resulted in key findings that show its value as a stand-alone study: 1) Nitrate concentrations are highest in the upper vadose zone and affected by texture. Those effects are not evident in the deeper vadose zone. 2) Vadose zone nitrate concentrations are affected by the crop grown. These results suggest an opportunity for lower legacy mass transport for grapes and higher legacy mass transport for both tomatoes and almonds. 3) Variability in individual farmers’ past and present fertilizer and water management practices contributes to different legacy salt and nitrate loads in the vadose zone. Data from the field study and other related and concurrent OFFCR field efforts were used during model development. The overall modeling approach was designed to model nitrate and salt transport for lands under OFFCR operation for different crop types, vadose zone characteristics and groundwater characteristics. The defined goals of this design and modeling approach were to: 1) model nitrate and salt movement through the vadose zone and into groundwater; 2) test the model against scenarios that consider different recharge rates, cultural practices, soil types, and depths to groundwater, assessing the timing and magnitude of loading through the vadose zone and the effects on underlying groundwater; and 3) recommend management practices to mitigate potential groundwater impacts. To achieve these goals, two models were integrated to simulate nitrate and salt transport through the vadose zone to groundwater under different scenarios: a 1D Hydrus model and an analytical groundwater model (AGM)