Management of Aquifer Recharge for Sustainability

Proceedings of the 4th International Symposium on Artificial Recharge of Groundwater, Adelaide, September 2002

P.J. Dillon

• Publisher: CRC Press
• Year: 2020
• ISBN:
  9781000151275
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

This title offers more than 100 papers originating in 20 countries, covering research on a widening range of methods for recharge enhancement and groundwater quality protection and improvement. These include: bank filtration; aquifer storage and recovery; and soil aquifer treatment, as well as rainwater harvesting and pond infiltration. The emphasis is on understanding subsurface process to improve siting, design and operation and to facilitate use of stormwater and reclaimed water, particularly in water-scarce areas.

Geochemistry of aquifer recharge

Quantifying the hydrogeochemical impact and sustainability of artificial recharge systems

P.J. Stuyfzand
Kiwa Water Research, Nieuwegein, Netherlands

ABSTRACT: A method is presented to predict and quantify the hydrogeochemical impact and sustainability of artificial recharge (AR) systems. Eight hydrogeochemical impacts are defined: the resulting pollution level in recharge(d) water (input and aquifer) and in soil (sludge and aquifer), the sludge accumulation rate and 3 leaching rates (leading to decalcification, oxidation and loss of sorption capacity, of the aquifer). Each impact is quantified by an index, which relates the actual state of the recharge system (either AR or river bank or natural) to the state in a similar, but clean natural background area. Combination of these 8 indices yields the hydrogeochemical sustainability index for which also a radar plot is presented.

The required data input consists of (a) quality of recharge water; (b) native hydrogeochemistry of target aquifer; (c) natural backgrounds; and (d) hydrological characteristics of the recharge system. The method is integrated in the expert model Easy-Leacher 4.6 (explained elsewhere in this volume), but can also be applied independently and in other background areas than the Netherlands.

1 INTRODUCTION

Important questions, when designing a new artificial recharge (AR) facility or optimizing or even defending an existing one, regard its resulting chemical or environmental impact and hydrogeochemical sustainability (definition in section 2.2). Good answers are crucial for getting or keeping the license, public acceptance, low operational costs on the long term, and the preferred quality of recovered water.

These answers can be given in advance, when we know enough about (a) the quality of water to be recharged; (b) the native hydrogeochemistry of the receiving aquifer system; (c) natural backgrounds; and (d) hydrological characteristics of the new or modified AR system. In that case we can assess the individual chemical impacts of the various recharge options, and somehow condense these impacts into a single hydrogeochemical sustainability index. This index can be used then as an unbiased chemical score, which should be included in every decision or evaluation system, together with the hydrological, ecological and financial scores.

In this contribution a method is presented to arrive at such a chemical score, by predicting and quantifying several individual chemical impacts of AR systems, and combine them into a single hydrogeochemical sustainability index.

The calculations involve the use of multicriteria pollution indices for water and soil, and application of the 2D reactive transport code Easy-Leacher® 4.6, details of which are given by Stuyfzand (2001, 2002). This model generates essential quality data regarding water and soil in the various compartments, the accumulation rate of sludge in recharge basins and the leaching rate of natural reactive phases in the aquifer matrix.

2 IMPACTS AND SUSTAINABILITY

2.1 Hydrogeochemical impacts

The hydrogeochemical impacts of AR consist of the following processes (Table 1): (a) raising the infiltration intensity and thereby also the load and flux of dissolved and suspended compounds through the surface water body and aquifer system; (b) displacement of the native groundwater and, if present, surface water by the infiltration water; (c) accumulation of more or different sludge in basins or ponds; (d) accumulation of more or other pollutants in sludge and aquifer; (e) enhanced chemical leaching of natural, reactive aquifer components like CaCO₃ (acid buffer), organic matter (redox buffer and sor-bent) and pyrite (redox buffer); (f) physical elution of fine aquifer particles (FAP, being a sorbent); and (g) accumulation of clogging material around the recovery system (iron(hydr)oxides and FAP).

After some time of recharge operation these processes typically occupy the zones indicated in Fig.l. Whether they create problems strongly depends on quality of the infiltration water, recharge and pumping rates, recharge management (like sludge removal), quantity and quality of rain water and atmospheric deposition, geochemistry of the aquifer system and natural backgrounds.

The result of processes a-e is quantified by the indices listed and explained in Table 1. Processes f and g are not yet considered by lack of knowledge.

2.2 Hydrogeochemical sustainability

AR operations are sustainable when all resulting beneficial processes are renewable and continue indefinitely, without undesirable effects on adjacent systems. The following criteria should be met in order to earn the mark “hydrogeochemically sustainable”: (1) the receiving aquifer system and, if present, recharge basins and recollection canals remain multifunctional (fit for other uses when AR operations should be abandoned); (2) the beneficial physical and (bio)chemical processes in the recharge facilities and receiving aquifer system continue indefinitely; (3) criteria 1 and 2 last as long as they last in adjacent or comparable background areas; and (4) recharge operations do not change the chemical environment of the adjacent area (including surface water and groundwater).

HydrogeoCHEmical SuStainability (CHESS) is mainly undermined by the processes listed in Table 1 and shown in Fig.l. CHESS can therefore be quantified by averaging the magnitude of their effects (section 6).

Table 1. The main processes which may affect the hydrogeo--CHEmical SuStainability (CHESS) of recharge systems, with numbering as in text. The parameter or index which is used to quantify the process or its resulting effects, is indicated. Marked are those processes which are included in the construction of the CHESS-radar plot (Fig.2). FAP = Fine Aquifer Particles; NOM = Natural Organic Material.

Process	Index	in CHESS-radar ??
a: INCREASING LOAD + FLUX	WAPIFLUX	yes
DISPLACEMENT of native:
b1 Surface water	WAPI	no
b2 Groundwater	WAPI	yes
ACCUMULATION of:
c: Sludge	SLAR	yes
d1 Pollutants in sludge	SOPI	yes
d2 Pollutants near basin banks	SOPI	no
d3 Pollutants in main aquifer	SOPI	yes
g Clogging material near recovery	−	no
LEACHING + ELUTION
e1 Decalcification	DECAR	yes
e2 Oxidation (NOM + FeS2)	OXIR	yes
e3 Loss of sorption capacity	LOSCA	yes
f : Elution FAP near recovery	−	no

WAPI = WAter Pollution Index (section 3.1); WAPI_FLUX = WAPI related to flux (section 3.2); SOPI = SOil Pollution Index (section 3.3); SLAR = SLudge Accumulation Rate (section 4); DECAR = DECAIcification Rate (section 5.1); OXIR = Oxidation Rate (section 5.2); LOSCA = Loss of Sorption CApacity (section 5.3).

Figure 1. Zoning of processes which undermine the hy...

Table of contents

• Cover
• Half Title
• Endorsing Organisations
• Title Page
• Copyright Page
• Table of Contents
• Foreword
• International review committee
• Keynote & Invited papers
• Sustainability of managed recharge
• Water quality changes in the subsurface
• Geochemistry of aquifer recharge
• Fate of pathogens
• Fate of organics
• Management of clogging
• Groundwater hydraulics and storage recovery
• Recharge enhancement in fractured rock
• Water reuse via aquifers
• Environmental applications of recharge projects
• Arid zone water management
• Injection well issues and solutions
• Pond and bank filtration issues and solutions
• Holistic urban water management
• Agricultural practices and recharge enhancement
• Regional issues and recharge site selection
• Author index
• International Association of Hydrogeologists Commission on Management of Aquifer Recharge