Equus Beds Recharge Project

The water supply for the city of Wichita, south-central Kansas, currently comes from the Equus Beds aquifer and Cheney Reservoir. Because these sources are not expected to meet projected city water needs into the 21st century (Warren and others, 1995), artificial recharge of the Equus Beds aquifer was investigated as one alternative to meet future water-supply demands. An additional potential benefit of artificial recharge includes preventing degradation of the water quality of the aquifer by saltwater plumes from the Arkansas River to the southwest and the Burrton oil field to the northwest (Ziegler and others, 1999). Phase I of the full-scale artificial recharge project began in 2007 and continued through 2012. Phase II became operational in April 2013 and has a design capacity of 30 Mgal/day.

Phase I of the full-scale artificial recharge project began in 2007 and continued through 2012. For Phase I, the water pumped directly from the Little Arkansas River was treated to reduce sediment and remove atrazine before being recharged to the aquifer through recharge basins; water pumped from wells in the riverbank did not receive additional treatment before being recharged to the aquifer through recharge basins or wells (Debra Ary, city of Wichita, written commun., 2012). Phase II recharge facilities withdraw water from the Little Arkansas River and treat the water using ultrafiltration membranes and advanced oxidation techniques. The treated water can then be recharged into spreading basins or recharge wells throughout the area and stored in the aquifer for future use. Phase I has a design capacity of 10 Mgal/day. Phase II became operational in April 2013 and has a design capacity of 30 Mgal/day. Total construction costs for Phase I and II were about $247 million.

Map of Operations for Equus Beds Groundwater Recharge Project

City of Wichita Aquifer Storage and Recovery Program:

http://www.wichita.gov/
http://www.wichita.gov/Government/Departments/PWU/Pages/WaterQuality.aspx

Water Quality

Expected effects of artificial recharge

Will increase water levels and storage in the aquifer
Will slow down southeast movement of chloride near Burrton and along the Arkansas River
As water levels increase, concentrations of some metals may temporarily increase until reaches geochemical equilibria
Recharge of oxygenated water will decrease concentrations of metals—as long as it remains oxygenated

Water-quality changes associated with Phase I & Phase II recharge

Kansas Underground Injection Control Area Permit Class V Aquifier Storage and Recovery, Kansas Permit No. KS-05-079-004
Water-quality Data Compilation for 2010-2016

What controls the water quality?

Chloride — proximity to Burrton and Arkansas River and possible dilution by recharge water or increased hydraulic head slowing the movement of the chloride plume
Arsenic, iron, and manganese — presence in aquifer materials, distribution of clays, chemically reducing conditions, and areas of larger water level declines
If oxygenated water is recharged into a reducing aquifer, concentrations of dissolved arsenic, iron and manganese will decrease because these constituents will precipitate from solution
Nitrate, atrazine, and bacteria in surface water, — controlled by runoff and agricultural land use

Chlorides

Chloride concentrations exceeded the SDWR of 250 mg/l in less than 8% of the shallow and deep parts of the aquifer. Crop yields decrease if concentrations >350 mg/L (Bauder and others, 2007).

Concentrations larger than 500 mg/L were found near Burrton, where previous oilfield brine disposal occurred. These brines have moved about 3 miles in the past 45 years. Also, large concentrations of chloride from the Arkansas River are moving into the aquifer because of ground water declines caused by agricultural and city pumping.

Chloride is moving……..slowly….. Phase 1 artificial recharge may have helped stabilize chloride concentrations from 2004 to 2010 and likely again in 2013. Concentrations increased in 2011 and 2012 due to curtailed recharge as a result of drought-related low flows in the Little Arkansas River, but corresponding with Phase I & II recharge activities: 2013 chloride concentrations are again showing signs of stability while ASR is operated.

Arsenic

Why is Arsenic an issue in the Equus Beds Aquifer?

There is an EPA Maximum contaminant level (MCL) of 10 micrograms per liter (ppb). Before 2006, the criterion was 50 ppb. Annual samples are required. If the criterion is exceed, then quarterly are required. The MCL is the annual average of the collected samples.
Background concentrations (before recharge) for arsenic exceeded 10 ppb in several wells and in the Little Arkansas River.
Arsenic is naturally present in the aquifer sediments.
Arsenic is controlled by the geochemistry of the aquifer material and the oxygen conditions in the aquifer.

http://water.usgs.gov/nawqa/trace/pubs/geo_v46n11/fig3.html

BASELINE (1995-2013) Arsenic concentrations in shallow groundwater (well less than 80 feet deep)

Arsenic concentrations exceed 10 ppb in 12% of samples
Arsenic concentrations exceeding 10 ppb are associated with low (no) oxygen, clays, and areas of water-level declines

BASELINE (1995-2012) Arsenic concentrations in deep groundwater

Concentrations exceed 10 ppb in 35 % of deep groundwater
Concentrations are controlled by low (no) oxygen, more clay, and possibly thicker aquifer

Computed dissolved arsenic concentration in the Little Arkansas River at Highway 50 near Halstead, KS

When streamflow exceeds 57 cfs, arsenic doesn’t exceed 10 ppb, therefore, arsenic in treated surface water is not a problem for artificial recharge.
From 1999-2012, Arsenic exceeded 10 ppb about 15% of time. However, due to low flows in 2013, computed arsenic concentrations exceeded 10 ppb about 75% of the time.

Arsenic variability is much greater than chloride variability.

General Geochemical controls for Arsenic

Minerals important for recharge and geochemistry
- Calcite (calcium carbonate)
- Pyrite (iron sulfide) (can contain arsenic)- Sources
- Iron hydroxides (both source and sink)
Controls
- Clays
- Oxygen (oxidation-reduction potential or Eh)
- Concentrations

Natural geochemical process of arsenic concentrations in an aquifer

Controlled by:
- Sources–clay-rich areas have more pyrite (and sorbed arsenic)
- Oxygen(or lack of oxygen); more oxygen = less dissolved arsenic
- Infiltrating water quality and receiving aquifer quality
What does this mean in the aquifer?
- Dewatered areas oxygenate and destabilize arsenic-containing pyrites
- Arsenic and iron are dissolved or leached
- As a result of increasing oxygen concentrations from either dewatering or the recharge of oxygenated water, amorphous iron oxides (hydroxides, oxyhydroxides) may form.
- Dissolved arsenic species can be scavenged by or sorb to the surfaces of precipitated iron oxide species, and are, therefore, removed from groundwater
- In summary, a new equilibrium is reached in the aquifer that is primarily controlled by oxygen availability

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Equus Beds Surface-Water Quantity Results

The source water for the Equus beds artificial recharge project is the Little Arkansas River. During the demonstration phase of the project through 2002, according to permit conditions set by the Kansas Department of Agriculture, Division of Water Resources, water could be diverted from the river for recharge under the following conditions:
- At the Halstead Recharge site, from April 1 through September 30, when streamflow at the USGS stream gage Little Arkansas River at Highway 50 near Halstead (07143672) exceeded 42 cubic feet per second (cfs).
- At the Halstead Recharge site, from October 1 through March 31, when streamflow at the USGS stream gage Little Arkansas River at Highway 50 near Halstead (07143672) exceeded 20 cfs.
- At the Sedgwick Recharge site, throughout the entire year, when streamflow at the USGS stream gage Little Arkansas River near Sedgwick, KS (07144100) exceeded 40 cfs.
Permit guidelines for Phase I and Phase II full scale recharge operations established by the Kansas Department of Agriculture, Division of Water Resources, in August 2005, require the following conditions for water to be diverted from the river for recharge:
- At the Halstead Recharge site, from April 1 through September 30, when streamflow at the USGS stream gage Little Arkansas River at Highway 50 near Halstead (07143672) exceeds 57 cfs.
- At the Halstead Recharge site, from October 1 through March 31, when streamflow at the USGS stream gage Little Arkansas River at Highway 50 near Halstead (07143672) exceeds 20 cfs.
- At the Sedgwick Recharge site diverted water shall not cause the streamflow at the downstream Valley Center (07144200) site to fall below 30 cfs.

Little Arkansas River at Highway 50 near Halstead, KS (07143672)

Little Arkansas River at Valley Center, KS (07144200)

Surface water quantity data is also available for:

More Real-Time Water-Quality information for Kansas is available at http://nrtwq.usgs.gov/ks/.

Site	Year	# of days when Q exceeded conditions	# of days when Q exceeded 70 cfs	# of days when Q exceeded 100 cfs
Little Arkansas River at Highway 50 near Halstead, KS (07143672)	1995	99	72	62
	1996	130	61	52
	1997	270	97	83
	1998	261	161	121
	1999	349	161	133
	2000	234	117	94
	2001	171	103	88
	2002	110	57	47
	2003	161	89	71
	2004	159	67	49
	2005	157	104	81
	2006	15	8	5
	2007	166	131	109
	2008	286	136	95
	2009	280	113	85
	2010	170	58	46
	2011	49	16	11
	2012	41	24	18
	2013	72	49	37
	Average	167	85	68
	Median	161	89	71
	Std. Deviation	93	45	36
	10th Precentile	47	22	17
	90th Percentile	281	141	111

Little Arkansas River at Valley Center, KS (07144200)	1995	316	146	127
	1996	343	119	96
	1997	365	178	139
	1998	325	286	255
	1999	365	300	272
	2000	309	215	150
	2001	322	158	138
	2002	291	89	76
	2003	312	124	111
	2004	366	134	106
	2005	361	184	164
	2006	172	25	18
	2007	265	165	152
	2008	361	255	192
	2009	365	188	164
	2010	365	181	108
	2011	184	34	27
	2012	117	50	43
	2013	233	86	74
	Average	302	153	127
	Median	322	158	127
	Std. Deviation	75	77	68
	10th Precentile	182	47	40
	90th Percentile	365	259	205

Equus Beds Groundwater Quantity Results

Substantial pumping of the Equus Beds Aquifer began in September 1940 resulting in a gradual decrease of the aquifer's water level. Water-level declines, of up to 40 feet in some areas, occurred by 1993 as a result of increased city and irrigation pumpage and the 1988-92 drought. The water level declines resulted in a loss of storage of almost 300,000 acre feet that was no longer available for water supply. This trend in water-level decline and loss of storage prompted the City of Wichita to reduce pumpage of the Equus Beds aquifer and initiate the Integrated Local Water Supply Program (ILWSP). The ILWSP, now referred to as the Equus Beds Aquifer Storage and Recovery (ASR) Program was designed to ensure an adequate water supply for the city by increasing reliance on other sources outside the study area (for example, Cheney Reservoir), encouraging conservation, and developing the Equus Beds ASR project. The purpose of the Equus Beds ASR project is to take water from the Little Arkansas River and store it in the aquifer. The water stored in the aquifer increases the amount of groundwater available for later use and raises water levels in the aquifer. These higher water levels slow down or prevent the movement into the central part of the study area (where the city has its production wells) of an oil-field brine plume near Burrton, Kansas, and of naturally occurring saline water in the Arkansas River. Wichita plans to annually recharge into the aquifer about 11,000 acre-feet (about 3.6 billion gallons) of water.

The benefit of the ASR program to the Equus Beds aquifer was seen in winter 2013 at the end of the recent 2011-12 drought. In the central part of the study area, water levels in winter 2013 were about 10 feet higher and storage volume about 51,000 acre-feet greater than in 1993. These recoveries occurred despite precipitation that was 25 percent less than average in 2011 and 2012, irrigation pumpage that increased to new record amounts, and almost non-existent artificial recharge in 2011 and 2012. With the return to more normal rainfall 2013, water levels rose more than an average of 1 foot and storage volume recovered more than 5,000 acre-feet in the central part of the study area. These and other findings can be found at http://pubs.usgs.gov/sir/2014/5185/

Changes in Groundwater Levels and Storage in the Equus Beds Aquifer, Northwest of Wichita, Kansas

Water Level, Continuous data and Historical Groundwater-level links for the Equus Beds Aquifer

Equus Beds Water-Quality Results

Baseline (before artificial recharge) sampling and during demonstration phase defined the constituents of concern (>5% of samples exceed water quality standards) for artificial recharge; (Surface Water detection table, Groundwater detection table) Sampling has continued to define the water quality of surface and groundwater.
Surface Water Summary Table
Groundwater Summary Table
A number of organic compounds have been detected, but no concentrations exceed water-quality standards.
Burrton Chloride plume has moved about 3 miles in past 45 years.
Chloride in Little Arkansas River exceeds 250 mg/L in <1-20% of samples.
Chloride in deep index wells exceeds 250 mg/L (SMCL) 8% of time—5% in shallow wells—with higher values near Burrton and along the Arkansas River.
Sulfate exceeds 250 mg/L (SMCL) in 18% of shallow and 13% of deep groundwater.
Nitrate exceeds 10 mg/L (MCL) in about 15% of shallow groundwater- little nitrate in deep groundwater.
Arsenic exceeds 10 ug/L (MCL):
- In surface water about 10% of samples and usually during low flow.
- In shallow groundwater in 12% of the samples.
- In deep groundwater in 34% of samples.
Atrazine concentrations in the Little Arkansas River exceed 3 ug/L in about 42% to 50% (MCL – as annual average) of the samples mostly in late spring through early fall.
- Atrazine is detected in 56% of shallow wells indicating infiltration from field application.
Coliform and E. coli are detected in nearly all surface water samples.
Total coliforms were detected in 25% of shallow index wells and 12% of deep index wells.

Chloride Summary

A number of organic compounds have been detected, but no concentrations exceed water-quality standards.
Burrton Chloride plume has moved about 3 miles in past 45 years.
Chloride in Little Arkansas River exceeds 250 mg/L in <1-20% of samples.
Chloride in deep index wells exceeds 250 mg/L (SMCL) 8% of time—5% in shallow wells—with higher values near Burrton and along the Arkansas River.
Sulfate exceeds 250 mg/L (SMCL) in 18% of shallow and 13% of deep groundwater.
Nitrate exceeds 10 mg/L (MCL) in about 15% of shallow groundwater- little nitrate in deep groundwater.
Arsenic exceeds 10 ug/L (MCL):
- In surface water about 10% of samples and usually during low flow.
- In shallow groundwater in 12% of the samples.
- In deep groundwater in 34% of samples.
Atrazine concentrations in the Little Arkansas River exceed 3 ug/L in about 42% to 50% (MCL – as annual average) of the samples mostly in late spring through early fall.
- Atrazine is detected in 56% of shallow wells indicating infiltration from field application.
Coliform and E. coli are detected in nearly all surface water samples.
Total coliforms were detected in 25% of shallow index wells and 12% of deep index wells.

Arsenic Summary

Before recharge, natural arsenic concentrations exceed the MCL of 10 ppb in 35% of deep groundwater, 12% of shallow groundwater, and in the Little Arkansas River 11% of the time since 1995.
Arsenic concentrations exceeding 10 ppb are associated with low (or no) oxygen, areas with more clay in the aquifer and areas where water levels have declined and are now recovering.
Increases in arsenic can be minimized by maintaining similar oxygen levels between the aquifer and recharge water.
If oxygen-rich water is recharged;
- iron and calcite likely will precipitate and may coat the aquifer materials,
- arsenic concentrations in the aquifer water will decrease if oxygen is maintained, improving the overall water quality in the aquifer will improve with respect to arsenic.

Equus Beds Recharge Project

Science Center Objects

Water-quality and geochemical variability in the Little Arkansas River and Equus Beds aquifer, south-central Kansas, 2001–16

Status of groundwater levels and storage volume in the Equus Beds aquifer near Wichita, Kansas, January 2016

Relations between continuous real-time physical properties and discrete water-quality constituents in the Little Arkansas River, south-central Kansas, 1998-2014

Effects of aquifer storage and recovery activities on water quality in the Little Arkansas River and Equus Beds Aquifer, south-central Kansas, 2011–14

Groundwater-level and storage-volume changes in the Equus Beds aquifer near Wichita, Kansas, predevelopment through January 2015

Water quality of the Little Arkansas River and Equus Beds Aquifer before and concurrent with large-scale artificial recharge, south-central Kansas, 1995-2012

Water quality of the Little Arkansas River and Equus Beds Aquifer before and concurrent with large-scale artificial recharge, south-central Kansas, 1995-2012

Status of groundwater levels and storage volume in the Equus Beds aquifer near Wichita, Kansas, 2012 to 2014

Preliminary simulation of chloride transport in the Equus Beds aquifer and simulated effects of well pumping and artificial recharge on groundwater flow and chloride transport near the city of Wichita, Kansas, 1990 through 2008

Revised shallow and deep water-level and storage-volume changes in the Equus Beds Aquifer near Wichita, Kansas, predevelopment to 1993

Irrigation trends in Kansas, 1991-2011

Simulation of groundwater flow, effects of artificial recharge, and storage volume changes in the Equus Beds aquifer near the city of Wichita, Kansas well field, 1935–2008