Assessing the performance of groundwater governance policies through lab and field experiments

Last registered on April 02, 2024


Trial Information

General Information

Assessing the performance of groundwater governance policies through lab and field experiments
Initial registration date
March 25, 2024

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
April 02, 2024, 10:50 AM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.



Primary Investigator


Other Primary Investigator(s)

PI Affiliation
ESI Medjez ElBab
PI Affiliation
INAT Tunis
PI Affiliation
CEEM University of Montpellier
PI Affiliation
CEEM University of Montpellier
PI Affiliation
CEEM CNRS University of Montpellier
PI Affiliation
CEEM INRAe University of Montpellier
PI Affiliation
G Eau Inrae

Additional Trial Information

In development
Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Rivalry in extractive CPR, like groundwater, implies that agents extract as much as they need, and even more if they fear that others behave the same way (Gardner et al., 1990; Walker et al., 1990 and 2000), leading to the ‘tragedy of the commons’ (Hardin, 1968). Users depleting a groundwater CPR typically face two types of appropriation externalities (Gardner et al., 1997): a static externality, whereby individuals’ extraction costs at any given date are affected by the total level of extraction at that date, and a dynamic externality, whereby the extraction cost any later date is affected by past cumulative extractions.

Groundwater is a very important source of irrigation water, the latter representing more than 70% of the total water uses on earth (FAO, 2022). In North Africa half of the current groundwater water withdrawals exceed natural rates of water recharge (Mayaux et al., 2022). Maghreb Countries are highly dependent on their groundwater resources for their agricultural development. The public policies of the last decades triggered radical changes in newly irrigated areas (extension areas) and in traditional oases (Kadiri et al., 2022). This resulted in a quick intensification of local agriculture, like in Tunisia, where oases are currently facing sustainability concerns due to “uncontrolled expansion of irrigated areas, overexploitation of groundwater resources, and soil degradation” (Ghazouani et al., 2009; Mekki et al., 2013).

In Tunisia, the Complex terminal aquifer in Kebili is under the threat of overexploitation, as its exploitation leads to a 1 metre lowering of the water table/year. This is due to the combination of a very low level of water recharge and high level of water use for irrigation mainly (Trigui et al., 2021).
In Tunisian oases, traditional farmers are organised in water users associations, called GDA (French acronym for Agricultural Development Groups), which coexist with newly settled extension farmers. Many GDA farmers also have plots in the extensions, where, like the extension farmers, they dig illicit private boreholes that are not declared to the local authority for water management (CRDA) (Farolfi et al., 2022).

Unregulated water extraction in the extensions is a major cause for groundwater overexploitation (Mekki et al., 2013), a situation that is likely to lead to the collapse of the system in the short or medium term. Urgent and drastic policy measures are therefore needed (Petit et al., 2017) to prevent such adverse outcome.

Current policies to match the problem are limited to the attempt by the CRDA to reduce access to water by limiting the number of boreholes. However, the overwhelming presence of illicit boreholes in Tunisian newly irrigated areas shows clearly the ineffectiveness of the measure. Alternative governance tools are necessary in order to face groundwater overexploitation in the Tunisian oases.

We address the issue of designing appropriate policy instruments to prevent overexploitation, based on laboratory experiments and lab-in-the-field experiments. Our aim is to compare several feasible instruments that can potentially be implemented in the field, by adopting a step-by-step experimental approach. We target particularly informational instruments (Tews et al., 2003) due to their lower cost compared to the complex administration often needed in order for command-and-control regulation to work properly or to implement and enforce economic instruments. We also observe the role of communication among CPR users to reduce overexploitation. In a first step, we will try to establish the effectiveness of the aforementioned alternative instruments to address the issue of overexploitation in a framed laboratory setting. This is done with standard student subjects, using the Montpellier Laboratory of Experimental Economics (LEEM) facility. In a second step, we replicate the standard laboratory experiments with Tunisian students of the National Institute for Agricultural Research in Tunis (INAT). The final step will be to replicate the lab experiment with Tunisian farmers directly involved in the exploitation of groundwater in the oasis of Jemna in Kebili region, in a lab-in-the-field setting. Step 1 will allow us to provide causal evidence of the effectiveness of the instruments and internal validity. Step 2 will allow us to control for the nationality of the student subjects and the robustness of the lab-findings according to location (Montpellier vs Tunis). The final step will provide external validity of the experimental findings of steps 1 and 2, following the methodology of Bchir (2014).

To this end, like Gardner et al. (1997), we designed laboratory experiments to assess the performance of various groundwater governance policies and the applicability of game theory to behaviour in such a system. We use the groundwater extraction dynamic model by Gardner et al. (1997) to run experiments in the lab (France and Tunisia) and in the field, with Jemna oasis farmers, in order to test the performance of various groundwater governance policies in the studied frame. The model implies a CPR recharge rate = 0, which is adapted to the local situation, as indicated by Trigui et al. (2021).

Bchir, M. A. (2014). From the lab to the field: An experimental investigation of the provision of a club good. Journal of Behavioral and Experimental Economics , 51, 57–67.
Dubois, D., S. Farolfi, P. Nguyen-Van, and J. Rouchier. 2020. "Contrasting effects of information sharing on common-pool resource extraction behavior: Experimental findings." Plos One no. 15 (10).
FAO. 2022. The State of the World’s Land and Water Resources for Food and Agriculture – Systems at breaking point. Main report. Rome.
Farolfi, S., Lavaine, E., Morardet, S., Lfakir, O., Khamassi, F., & Willinger, M. (2022). Farmers’ perceptions of water management in Jemna oasis, Southern Tunisia. New Medit, 21(5).
Gardner, R., Moore, R., and Walker, J. 1997. “Governing a groundwater commons: a strategic and laboratory analysis of western water law.” Economic Enquiry (35): 218-234.
Gardner, R., Ostrom, E., and Walker, J.M. 1990. "The Nature of Common-Pool Resource Problems." Rationality and Society no. 2 (3):335-358.
Ghazouani, W., Marlet, S., Mekki, I. and Vidal, A. (2009). "Farmers' Perceptions and Engineering Approach in the Modernization of a Community-Managed Irrigation Scheme. A Case Study from an Oasis of the Nefzawa (South of Tunisia)." Irrigation and Drainage 58: S285-S296. doi: 10.1002/ird.528
Hardin, G. 1968. "The Tragedy of the Commons." Science (162):1243-1248
Kadiri, Z. , Benmihoub, A., Farolfi, S., Khamassi, F., and Faysse, N. (2022)“Making Sense of On-Going Dynamics and Innovations in Oases and Newly Irrigated Areas of North African Arid Regions: Towards More Sustainable Development Pathways.” New Medit, vol. 21, no. 05, 20 Dec. 2022, 10.30682/nm2205n..
Mekki, I., Jacob, F., Marlet, S. and Ghazouani, W.. (2013). "Management of groundwater resources in relation to oasis sustainability: The case of the Nefzawa region in Tunisia." Journal of Environmental Management 121: 142- 151.
Mayaux, L.P., Lejars, C., Farolfi, S., Adamczewski-Hertzog, A., Hassenforder, E., Faysse, N., Jamin, J.Y. 2022. Enabling institutional environments conducive to livelihood improvement and adapted investments in sustainable land and water uses. SOLAW Background Thematic Report. Rome, FAO.
Petit, O., Kuper, M., Lopez-Gunn, E., Rinaudo, J. D., Daoudi, A. and Lejars, C. (2017). "Can agricultural groundwater economies collapse? An inquiry into the pathways of four groundwater economies under threat." Hydrogeology Journal 25 (6): 1549-1564. doi: 10.1007/s10040-017-1567-3.
Tews K., Busch P-O., Jörgens H., 2003. The diffusion of new environmental policy instruments. European Journal of Political Research, 42: 569-600.
Trigui M.R., Trabelsi R., Zouari K., Agoun A., 2021. Implication of hydrogeological and hydrodynamic setting of water quality in the Complex Terminal Aquifer in Kebili (southern Tunisia): The use of geochemical indicators and modelling. Journal of African Earth Sciences, 176: 104121. https://doi. org/10.1016/j.jafrearsci.2021.104121.
Walker, J. M., R. Gardner, and E. Ostrom. 1990. "Rent Dissipation in a Limited-Access Common-Pool Resource - Experimental-Evidence." Journal of Environmental Economics and Management no. 19 (3):203-211. doi: Doi 10.1016/0095-0696(90)90069-B.
External Link(s)

Registration Citation

Dubois, Dimitri et al. 2024. "Assessing the performance of groundwater governance policies through lab and field experiments ." AEA RCT Registry. April 02.
Experimental Details


Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
We assess through laboratory and field experiments the performance of various groundwater governance policies to reduce over-exploitation of groundwater CPR. We analyse the role of communication among players to reduce over-exploitation of groundwater CPR.
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
We observe if players' myopic behaviour increases over-exploitation of groundwater CPR.
We observe whether field actors' (farmers) behaviour is different from university students' behaviour.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
The following hypotheses are tested:

H1: In the absence of a governance policy (baseline condition of ‘laissez faire’), the appropriation externalities push players to assume a behaviour conducing to a Nash equilibrium.

H2: The introduction of governance policies based on informational instruments reduces the depletion rate of the CPR, bringing the system closer to the Social optimum.

H3: Communication among players contributes to bringing the system closer to the Social optimum.

To test these hypotheses, four Treatments were designed:
T0 (Baseline)
T1 (Simulator)
T2 (Communication + Simulator)
T3 (Expert Advice + Simulator)

In the baseline treatment (T0), players dispose only of a calculator facilitating their extraction choice at every given period.
In the simulator treatment (T1), players dispose of a calculator allowing them to make simulation over all rounds missing before the end of the session (5-t where t = current round). This simulator is a proxy of more information available to players about the consequences of dynamic extractions of the CPR on the CPR availability and subsequent extraction costs. As we can keep record of the use of the simulator by players, this treatment also allows observing the attitude by certain players to investigate dynamic externalities (sophisticated players looking at future extractions) in comparison with myopic players that are interested only in static externalities.
In the communication treatment (T2), players have the calculator like in T1 and in addition can chat (cheap talk) during 2 minutes before rounds 1, 3, and 5 in sequence 2.
In the Expert Advice treatment (T3), players have the calculator like in T1 and T2, and in addition receive every round a suggestion about the global amount of CPR to extract in order to maintain the social optimum in the group.

The model is the same as in Gardner et al., (1997), with groups of 5 players that can extract up to 25 tokens each at every round.

The experimental protocol involves three parts (sequences) of 5 rounds each per session. The first sequence is a training session not remunerated. The second session is always the baseline (T0), whilst the third sequence is a treatment (T0 to T3). In total 15 rounds are played. The experimental design is summarized as follows:
Sessions: Baseline, Simulator, Communication + Simulator, Expert Advice + Simulator
Sequence 1: Rounds 1-5 (Training)
Sequence 2: Rounds 6-10 (T0)
Sequence 3: Rounds 11-15 (T0, T1, T2, T3)
Groups & participants per session: 12 Groups 60 Participants
This experimental protocol will be run twice in the lab (Montpellier and Tunis), and once in the field, with farmers in the Jemna oasis, South Tunisia. A total of 240 x 3 = 720 participants is expected.

Empirical strategy
We use a difference-in-differences estimation to identify the effect of the introduction of policy measures relying on variation in the level of extraction both across groups and over sequences. Extraction levels are compared before and after policy implementation in treated groups with the extraction level of the baseline groups without policy.
Experimental Design Details
Not available
Randomization Method
In France, the sessions will be conducted in the Laboratory of Experimental Economics in Montpellier (LEEM). The participants are students from various disciplines of the university of Montpellier randomly selected from a pool of nearly 3,000 volunteers handled with the Online Recruitment Software for Economic Experiments (ORSEE).
In Tunisia, Lab experiments will be conducted at the National Institute for Agronomy in Tunis (INAT) The participants are students from INAT and various disciplines of the university of Tunis Cartage randomly selected from a pool local students. Field experiments will be conducted in the Jemna oasis. The participants are farmers randomly selected from a pool of nearly 2,600 farmers in the oasis, with the help of the local association for the protection of the Jemna oasis.
Randomization Unit
Sessions of 20 participants (4 groups, N =5) will be run.
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
24 sessions in the lab; 12 sessions in the field
Sample size: planned number of observations
720 players
Sample size (or number of clusters) by treatment arms
The experimental protocol is composed of 3 sessions/treatment, for a total of 12 sessions
(240 participants). Each session runs with 20 participants (4 groups). Thus, each treatment
will have 60 participants (12 groups).
It will be run twice in the lab (Montpellier and Tunis), and once in the field, with farmers in the
Jemna oasis, South Tunisia. A total of 240 x 3 = 720 participants is expected.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Supporting Documents and Materials

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Institutional Review Boards (IRBs)

IRB Name
CEE-M’s Internal Ethics Committee
IRB Approval Date
IRB Approval Number