Recipient Organization
COLORADO STATE UNIVERSITY
(N/A)
FORT COLLINS,CO 80523
Performing Department
Civil and Environmental Engineering
Non Technical Summary
Earthen canals are the most basic and prevalent method of conveying water for agricultural uses. Unfortunately, unless preventative measures are taken, earthen canals typically leak substantially. Seepage losses have been estimated to average 37% in unlined canals across the western United States. Seepage results in substantial water loss, degradation of down-watershed water quality, and crop damage. Not only is water lost as seepage unavailable for intended agricultural uses but seepage increases local groundwater elevations resulting in elevated groundwater upflux which contributes to waterlogging and salting of fields and decreased crop yields, along with non-beneficial water consumption from fallow and naturally-vegetated areas. Canal seepage also mobilizes geogenic salts and trace elements, along with nutrients percolating from fields, to surface water bodies, reducing water quality. It is crucial that water managers do better in controlling canal seepage which has been identified as a principal best management practice for preserving both water quantity and quality in agriculture.Numerous methods are available to reduce canal seepage, including permanent liners (e.g., concrete, plastic "geomembranes") and less-permanent sealants (e.g., bentonite clay, water soluble polymers). Concrete liners have been shown to reduce seepage by 50-97% and can have a life span ranging from 20-60 years. However, there is a large up-front capital cost associated with permanent liners, along with on-going maintenance costs, that can exceed available financial resources in many applications. In addition, permanent liners are difficult to deploy or remove as water availability varies. Sealants provide a more palatable alternative for seepage mitigation in many circumstances, largely due to lower up-front costs and the ability to regulate seepage mitigation on an as needed basis.Low-cost linear anionic polyacrylamide (LAPAM), a petroleum-based polymer that dissolves rapidly in water, has been shown to be effective for temporary (e.g., one water season) seepage control in earthen canals and ditches at both the lab and field. Research has shown that granular LAPAM applied via boat to a flowing canal yields a 28 to 87% reduction in seepage when applied under favorable conditions; however, when applied under unfavorable conditions, zero seepage reduction was measured. Despite the promise of LAPAM as a sealant, two primary factors have hindered its use. First, there is a negative perception by some against the introduction of a synthetic polymer into agricultural water supplies. The acrylamide monomer from which LAPAM is produced is a known toxin and carcinogen. Although LAPAM is produced to contain minimum residual acrylamide monomer, a low quantity inherently remains. When LAPAM was excessively applied, or applied under unfavorable conditions, residual monomer, though in low concentrations (typically below EPA maximum thresholds), was detected in downstream waters. Although greener biopolymer alternatives to LAPAM, have been known for 60-plus years, limited research exists identifying specific (optimal) biopolymers and we are unaware of any field-scale studies of the effectiveness of biopolymers for reducing seepage from canals. In addition, recent advances in biotechnology have provided tools to more economically produce specific biopolymers at commercial scales. Second, there is limited information on best practices for polymer sealant applications to canals. Although some initial (academic level) recommendations have been developed, there is not an accessible resource for describing how and when to use polymer sealants that is readily accessible to water managers.The goal of this project is to develop and to document guidelines for the use of biopolymer sealants for effective canal seepage reduction in the field to increase water conservation and water delivery efficiency and to decrease associated agro-environmental damages. This project will (1) use CSU-developed laboratory apparatus toidentify biopolymers effective for sealing earthen canals under soil and water conditions representative of Colorado field locations; (2) conduct field-scale demonstrations of effective canal sealing with laboratory-identified biopolymers, and simultaneously refine and document the application methodology; and (3) prepare advice that is targeted at water managers throughout Colorado to manage canal seepage through a first generation of an easy-to-understand guide (version 1.0) on the benefits and procedures of using polymer sealants, with a focus on biopolymers, to manage canal seepage.
Animal Health Component
25%
Research Effort Categories
Basic
(N/A)
Applied
25%
Developmental
75%
Goals / Objectives
The goal of this project is to develop and to document guidelines for the use of biopolymer sealants for effective canal seepage reduction in the field to increase water conservation and water delivery efficiency and to decrease associated agro-environmental damages. Specific objectives of the processed research are:Objective 1 (O1): Use a CSU-developed laboratory infinity flume to identify biopolymers effective for sealing earthen canals under soil and water conditions representative of Colorado field locations.Objective 2 (O2): Conduct field-scale demonstrations of effective canal sealing with laboratory-identified biopolymers, and simultaneously refine and document the application methodology.Objective 3 (O3): Prepare advice that is targeted at water managers throughout Colorado to manage canal seepage through a first generation of an easy-to-understand guide (version 1.0) on the benefits and procedures of using polymer sealants, with a focus on biopolymers, to manage canal seepage.
Project Methods
Task 1: Measure current seepage losses along candidate test reaches of the Poudre Valley Canal and the Larimer & Weld Canal in Colorado's South Platte River Basin to characterize existing seepage losses (in support of O2).The flowing mass-balance method (Alam and Bhutta 2004, Martin and Gates 2014). In brief, the inflow-outflow method uses a volume balance procedure to calculate seepage rates with inflows, outflows, and storage changes directly measured. Seepage, QS, per unit length of the canal is calculated using the following equation (ANCID 2003).QS = QUS - QDS + QL + QP - QD - QE - DS/Dtwhere QUS is the canal inflow rate through the upstream cross section, QDS is the canal outflow rate through the downstream cross section, QL is the total rate of any lateral inflows along the canal reach, QP is the total rate of precipitation along the canal reach, QD is the total rate of outflow diverted along the reach, QE is the total rate of evaporation from the water surface along the reach, and DS/Dt is the rate of change of stored water within the canal reach. Close coordination with canal operators will allow tests to be conducted during periods when QL and QD are eliminated or minimal and testing is targeted to times without QP. Flow rates are measured with current meters and canal water level changes are measured with pressure transducers mounted in stilling wells installed at intervals along the canal.Testing will be conducted following the method described in Martin (2015) along 2- to 5-plus km canal reaches. Study locations will be selected such that the canal segments have minimal diversions. Multi-kilometer study reaches are necessary to encompass seepage quantities large enough to effectively overcome measurement errors during testing. Seepage measurements will be conducted by simultaneously measuring QUS, QDS, calculating DS/Dt using pressure transducer and canal geometry data, calculating QE using local climatic data, and coordinated with canal managers such that QL and QD are zero and choosing test times where QP is forecast to be zero.Task 1 will be completed in year 1 and used to support meeting Objective 2. Understanding existing (pre-treatment) seepage loss rates will be used to build support for biopolymer canal sealing activities during years 2 and 3.Task 2: Identify a candidate biopolymer for use in field scale testing.Laboratory work will be used to identify a biopolymer effective for reducing seepage on a level similar to LAPAM under conditions representative of the test reaches of the Poudre Valley Canal and the Larimer & Weld Canals studied in Task 1. Representative bed-soil and sediments will be collected from canal test reaches in the field for use in controlled laboratory tests. Bed soil visually characterized in the field as 'coarse' and 'fine' will be collected from each canal (total of four soils). Candidate biopolymers shall be natural-based or naturally occurring, relatively low cost, or have potential for future production at relatively low cost, rapidly disperse in water, and nontoxic.Preliminary screening of candidate biopolymers will be performed in 1D infiltration columns in which the hydraulic conductivity of the sediment is measured before and after polymer treatment. The improvement in hydraulic conductivity from a given polymer will be compared to LAPAM to gage polymer effectiveness at a similar treatment level. Biopolymers that exhibit performance similar to LAPAM will be tested in a laboratory infinity flume (which simulates a flowing canal section). The infinity flume allows seepage measurements on bed soils with flowing water, enabling better simulation of the physics in a flowing canal relative to a 1D column. Total suspended solids will be varied over the range observed in the canals during Task 1; additional variables will not be explored as part of this work due to the limited project budget, and focus will be on developing a guide based on our current level of knowledge for polymer-based canal sealing. Improved performance of a given biopolymer at a given dosing, in relation to LAPAM, will be confirmed via the infinity flume. Additional tests will then be performed to identify the optimal polymer treatment level.Task 2 will be completed in year 1 and be used to supports meeting Objective 1. Based on Task 2, a biopolymer will be selected for field study in year 2. If a biopolymer cannot be identified in year one that performs on the same level as LAPAM, a combination of biopolymer and LAPAM will be selected, as has been successfully demonstrated in laboratory columns by Lentz (2015).Task 3: Demonstrate the effectiveness of candidate biopolymer for canal sealing.Field testing will be used to demonstrate the effectiveness of the identified candidate biopolymer and provide the first field-scale demonstration (to our knowledge) of the use of a biopolymer for canal sealing at the field scale. Treatment and seepage measurement will be conducted following the method described in Martin and Gates (2014), Martin (2015), and Susfalk et al. 2008. Reaches identified in Task 1 will be targeted for treatment if determined to have a sufficient seepage to overcome measurement errors. Field measurements of seepage following biopolymer application will be compared to pre-application conditions. For further purpose of comparison, LAPAM may also be applied on or near treatment reaches at a different time and the measured post-treatment seepage compared to pre-application conditions and to conditions following biopolymer treatment. The PI and co-PI will use data collected in Tasks 1 and 2 to make the case for additional resources (polymer, labor) to enable larger-scale testing from the canal companies on which the seepage characterization was conducted. Field work will focus on developing and documenting field-implementable guidelines for best practices and procedures (in support of meeting Objective 3).Task3 will be completed in year 2 and will be used to support meeting Objectives 2 and 3.Task 4: Development of an initial version of a manual for use of biopolymers to manage canal seepage.Based on existing experience of the project team, additional experience developed through Task 3, and coarse method descriptions in Susfalk et al. 2008, a draft initial version of a manual for use of biopolymers to manage canal seepage will be developed. We envision and approximately 20-page guide that relies heavily on pictures and schematics and that includes at least the following aspects.Brief description of the nature of seepage losses from earthen canals, including influencing factors.Quantification of seepage losses from earthen canals.Qualitative description of the agro-environmental effect of canal seepage.Description of polymer-based canal sealing.Description of biopolymer-based canal sealing.Description of the materials needed for biopolymer-based canal sealing.Description of methods to deploy biopolymer sealants.Task 4 will be completed in years 2 and 3 in support of meeting Objectives 2 and 3.Task 5: Trial implementation of draft guide.Biopolymer treatment will be performed on the Poudre Valley Canal and the Larimer & Weld Canals by canal company employees based on methodology provided in the draft guide (generated in Task 4) to test both the guide and provide a second round of field tests to evaluate the effectiveness of biopolymer canal sealing. The project team will observe treatment, discuss shortcomings and gaps of the draft guide with the canal company employees, and quantify treatment effectiveness.Task 5 will be completed in year 3, in support of meeting Objectives 2 and 3.Task 6: Refine draft guide.The draft initial version of the manual will be revised based on lessons learned in Task 5.Task 6 will be completed in year 3 to meet Objective 3.