The challenges and complexities of ensuring a sustainable water supply and meeting future demand have been recognized and documented in numerous studies. The Colorado River Basin Water Supply and Demand Study performed by the U.S. Bureau of Reclamations (BofR Study)1 provides a good assessment of the developing situation in the Southwestern United States. Many of the specific challenges affecting this area are typical of those facing populations in arid and semi-arid regions throughout the world. Therefore, the BofR Study has relevance beyond this specific region.

At Manzanita Solutions, we have developed IPR as a new means to increase the regional water supply. Traditional approaches tend to be more expensive and have other associated drawbacks as well. Since IPR is meant to be an alternative approach, a few of the existing primary options and strategies are described below.

Traditional approaches to managing increasing water demand

The BofR study was extremely comprehensive, describing in detail many proposed solutions to ensure water security for the Southwestern United States. Each option was appraised based on a number of factors including cost, feasibility, amount of time required for analyses and implementation, and potential water yield. These evaluations are discussed in Appendix F of the report. Assessments of drawbacks for the primary options are summarized below.

 1)  Conservation of currently available but limited water supplies

This option comprises industrial and municipal water conservation. It is focused on reducing the regional water demand. Measures typically include activities such as enhanced public education and outreach, tiered levels of voluntary and mandatory restrictions, short-term rationing, and short-term water rate increases. Other measures include conservation-oriented plumbing and building codes, high efficiency faucets, fixtures and appliances, low-flow toilets, meter retrofits, efficiency in industrial processes and cooling, etc. Not included in this approach are water use restrictions that may be used as a local response to short-term drought.

Conservation of agricultural water can also be considered as part of this approach; however, a whole range of legal, political and economic factors must then be considered as well.

There is a limit to how much regional water demand can be reduced, however. Significant water conservation measures have already been applied in many urban centers over the past few decades, which reduces the potential for water savings and tends to increase the cost of further conservation measures. Much of the costs for this option are for public awareness and education, incentive plans, and administrative expenses.

2)  Improved management of currently available but limited water supplies

Similar to conservation, this option focuses on reducing the regional water demand. This entails improvements to reservoir operations, evaporation control covers over reservoirs and canals, and pumped groundwater storage. Also proposed are market-based approaches for water trades between end users, changes to current apportionment, and measures to limit regional population and economic growth. These introduce a whole range of legal, political and economic factors that must be considered, which may limit their implementation. This option also has a limit on how much regional water demand can be reduced. The expected return on investment (according to the BofR study) for this option tends to be rather low.

3)  Importing from outside sources

This option involves river and other out-of-Basin freshwater imports to increase the overall water supply, and includes several approaches:

  • Diverting water from other rivers using pipes, canals and pumping stations – this approach has been fairly well developed and applied in the past. Water from headwaters of other rivers nearby are diverted to the river serving the arid region. This requires large up-front capital and ongoing maintenance costs for the diversion facilities and infrastructure. Also, this reduces the water supply in the region served by the diversion source. There may be additional environmental, legal and commercial impacts that must be addressed and resolved before this plan may be implemented.

  • Transporting water from a source by ocean pathways – This approach conveys fresh water from the mouth of a large river, either by tanker ship or sub-ocean pipeline. Local water supplies near the source aren’t expected to be reduced by this approach, since any water entering the ocean can be considered surplus. Since this approach hasn’t been used on this scale before, there is uncertainty whether it is feasible or economically sound. If developed, large upfront capital and ongoing maintenance costs would be required for an extensive transport/conveyance system, as well as the complex facilities and operations required to integrate the imported water within the current water supply system. In addition, energy intensive pumping stations would be required to transport water further inland. There may be environmental impacts created by the new facilities, as well as the reduced flow of fresh water into the ocean at the source.

  • Towing icebergs to a distribution center – With this approach, icebergs would be towed by tugboats to a processing facility on the coast of the arid region. This idea has been around for well over 100 years in some form or another2, however it has only been tested for small-scale or special applications. Like the previous approach, there is uncertainty whether it is feasible or economically sound. If developed, large upfront capital and ongoing maintenance costs would be required for the complex facilities and operations required to integrate water from the iceberg within the current water supply system. Specialized tug boats would need to be developed, as well as the technology for processing the ice. In addition, energy intensive pumping stations would be required to transport water further inland. There will probably be environmental impacts created by bringing such large masses of ice near the coast where it is processed.

Each of these approaches requires addressing relevant permitting, legal, and policy issues. Implementation challenges for these options include raising significant capital, and meeting required environmental regulations. Imports via ocean routes require extensive energy or fuel and therefore have long-term viability challenges as well.

4)  Desalination

This option involves removing salt from currently unusable water sources to make it potable. These sources include ocean water, agricultural drain water and brackish groundwater. Desalination of ocean water requires extensive permitting, legal and compliance efforts. There is a limited amount of agricultural drain water and brackish groundwater available to desalinate. Each option requires complex facilities, and pumping stations to transport water to where it is needed. Desalination typically requires significantly more energy (for both processing and pumping) than other options assessed in the study. In addition, there are environmental challenges posed by the brine produced by the plants, which require additional mitigation efforts.

5)  Grey-water recycling

Grey water is generally defined as untreated wastewater that has not been contaminated by any toilet discharge, has not been affected by unhealthy bodily wastes, and does not present a threat from contamination by unhealthful processing, manufacturing, or operating wastes. This option was considered only for non-potable use. It should also be noted that grey water becomes biologically equivalent to “black water” (raw sewage) fairly quickly if it isn’t treated effectively. Grey water is often diverted back to regional rivers that are part of the supply system, so this option may not result in a net increase to the water supply.

6)  Rainwater Harvesting

This option is more of a “grass-roots” approach which considers how individual household rainwater harvesting can increase local supply in some areas. While this option is easy to implement, there are high capital costs to be paid by each household, which may limit actual adoption by the general public. Additionally, this option typically reduces the water supply downstream of the users.

7)  Sewage Recycling

Direct recycling of processed sewage for potable water is also a potential solution, however it was not considered by the BofR study. A sewage effluent recycling plant was built in Orange County, California at a cost of $481 million (The Orange County Water District, Ground Water Replenishment System – GWRS). Ongoing costs are about $850 per acre-foot, which is lower than current costs to import water (reference 3). This plant can produce up to 100 million gallons of water per day, based on available supply of sewage effluent, and represents a consistent source of additional water for the Orange County region. Local laws, permitting, financing and public perception may create challenges for developing reprocessing plants in other locations, however.

Summary

Table 1 contains a summary of upfront and recurring costs listed in the study, along with those for the Orange County recycling plant. This list is not exhaustive, but is representative of the options traditionally considered to manage increasing water demand. As can be seen, expected costs are high, and a relatively long development period is associated with most options. Increasing the water supply by increasing regional precipitation through IPR is intended to supplement and potentially compete with these more traditional approaches.

Table 1: Development and operating costs of various projects to increase water supply

Table 1: Development and operating costs of various projects to increase water supply

Note:  Cost estimates from the BofR study were projected using standard costing models. Costs for the Orange County Recycling Facility comes from financial data. Annual costs have been normalized to US dollars / acre-foot / year to allow rough comparisons between the different options, which feature large variations in scale and capacity.

  1. U.S.Bureau of Reclamations. (2011) Colorado River Basin Water Supply and Demand Study. Web, Retrieved Sep 9 2018, from http://www.usbr.gov/lc/region/programs/crbstudy/finalreport/.

  2. Madrigal, Alexis (2011) “The Many Failures and Few Successes of Zany Iceberg Towing Schemes. Aug 10, 2011. Web, Retrieved Oct 3 2018, from https://www.theatlantic.com/technology/archive/2011/08/the-many-failures-and-few-successes-of-zany-iceberg-towing-schemes/243364/

  3. Orange County Water District, Ground Water Replenishment System (GWRS). Web, Retrieved Sep 9 2018, from http://www.ocwd.com/gwrs