We formulate a hydro-economic model of the NorthWestern Sahara Aquifer System (NWSAS) to assess t... more We formulate a hydro-economic model of the NorthWestern Sahara Aquifer System (NWSAS) to assess the effects of intensive pumping on the groundwater stock and examine the subsequent consequences of aquifer depletion. This large system comprises multi-layer reservoirs with vertical exchanges, all exploited under open access properties. We first develop a theoretical model to account for relevant features of the NWSAS by introducing, in the standard Gisser-Sanchez model, a non-stationary demand and quadratic stock-dependent cost functions. In the second step, we calibrate parameters values using data from the NWSAS over 1955-2000. We finally simulate the time evolution of the aquifer system with exploitation under an open-access regime. We specifically examine time trajectories of the piezometric levels in the two reservoirs, the natural outlets, and the modification of water balances. We find that natural outlets of the two reservoirs might be totally dried before 2050.
Species' interactions and the involvement of shermen in several sheries may not be properly accou... more Species' interactions and the involvement of shermen in several sheries may not be properly accounted for by regulatory schemes, thus making regulation suboptimal. Being the only implementable instruments, the degree of ineciency of three second-best instruments is assessed (by using a bioeconomic multispecies model) in terms of their ability to get close to socially optimal eort and stock levels. The type of regulation and the existing biological interaction are also shown to result in dierent impacts on eort reallocation: a specic regulation does not necessarily increase the pressure on the unregulated species. Finally, we discuss how the choice of which second-best policy to implement is situation-specic.
drop of rainwater against a drop of groundwater: does rainwater harvesting really allow us to spa... more drop of rainwater against a drop of groundwater: does rainwater harvesting really allow us to spare Groundwater?
This paper studies groundwater management in the presence of rainwater harvesting (RWH). We propo... more This paper studies groundwater management in the presence of rainwater harvesting (RWH). We propose a two-state model that takes into account the standard dynamics of the aquifer and the dynamics of the storage capacity and we assume that the collection of rainwater reduces the natural recharge. We analyze the trade-o¤ between these two water harvesting techniques in an optimal control model. In particular, we show that when these techniques are pure substitutes, the development of RWH leads in the long run to a depletion of the water table even if pumping is reduced.
This paper studies a specific class of common-pool resources whereby rivalry is not characterized... more This paper studies a specific class of common-pool resources whereby rivalry is not characterized by competition for the resource stock. Artesian aquifers have been identified as a typical example, since the stock is never depleted, even when part of the resource is extracted. We first propose a dynamic model to account for relevant features of such aquifers-like water pressure, or well yield-and to characterize the corresponding dynamics. We then compare the social optimum and the private exploitation of an open-access aquifer. The comparison of these two equilibria allows us to highlight the existence of a new source of inefficiency. We refer to this as pressure externality. This externality results in the long run in an additional number of wells for the same water consumption, and hence additional costs. Finally, we characterize a specific stock-depend tax to neutralize the pressure externality. JEL Classification: H21, H23, Q15, Q25, C61
Species' interactions and the involvement of fishermen in several fisheries may not be proper... more Species' interactions and the involvement of fishermen in several fisheries may not be properly accounted for by regulatory schemes,thus making regulation suboptimal. Being the only implementable instruments, the degree of ineffciency of three second-best instruments is assessed (by using a bioeconomic multispecies model) in terms of their ability to get close to socially optimal effort and stock levels. The type of regulation and the existing biological interaction are also shown to result in different impacts on effort re-allocation: a specific regulation does not necessarily increase the pressure on the unregulated species. Finally, we discuss how the choice of which second-best policy to implement is situation-specific.
For a few decades, a growing literature has examined the role of water resources in interstate co... more For a few decades, a growing literature has examined the role of water resources in interstate con icts. In line with this literature, this study analyzes the risk of a con ict between countries sharing freshwater. While some scholars claim that waterbased con icts can never occur, this analysis determines this risk by linking it to the size of a negotiation interval; the probability-to-con ict decreasing with this size. In fact, we are going to show that the size of this interval diminishes with scarcer resources and with the degree of the heterogeneity of countries measured by their productive e ciency. Then, in a peace scenario, we determine by bargaining the optimal allocation and we study its variation according to the parameters of the model. These theoretical results will be con rmed by an econometric approach.
This paper is concerned with discrete choice contingent value estimate when the respondents are u... more This paper is concerned with discrete choice contingent value estimate when the respondents are uncertain about the environmental amenities. Within a class of indirect utility functions often used in empirical studies, the authors put forwards the effect of the risk premium on the willingness to pay (WTP). Then, it is shown how this risk premium also modi es the estimation procedure. A Monte Carlo simulation concludes the paper by putting forward a misestimation of the WTP. When this uncertainty is ignored, more precisely, the authors focus on the effect of the risk premium.
We examine theoretically a system of spatial property rights over a mobile re- newable resource. ... more We examine theoretically a system of spatial property rights over a mobile re- newable resource. The resource grows and is harvested in each area, but harvest in one patch imposes an externality on other patches through resource movement. This externality gives rise to over-extraction by non-cooperative patch owners. We propose a new institutional arrangement to internalize this externality. The in- strument involves granting limited-duration tenure, with the possibility of renewal, to each of the N interconnected concessionaries. Renewal of concession i is predi- cated on concessionaire i having never driven the stock below a pre-defined target Si. We show that not only can this instrument improve upon the decentralized property right solution, but under general conditions it can replicate the socially optimal extraction in every patch and every time period, in perpetuity. The dura- tion of tenure and the dispersal of the resource play pivotal roles in whether this instrument achie...
However, the economic rationale for groundwater management has been widely questioned since the s... more However, the economic rationale for groundwater management has been widely questioned since the seminal work of Gisser and Sánchez on the small benefits from regulation. Competitive extraction occurs where there is no regulation, i.e. where a limited number of groundwater users privately exploit the resource and each individual user ignores the impact of her pumping on others and on the overall state of the resource. Sometimes this is referred to as the “free-market scenario”. Optimal extraction refers to an optimal control scenario where a social planner maximizes the social welfare for all users. Many studies have argued that there may be no significant difference between competitive and optimal pumping rates. This result is now known as the Gisser-Sánchez Effect (GSE).
We consider groundwater managed by a sole owner and where a perfect substitute, rainwater harvest... more We consider groundwater managed by a sole owner and where a perfect substitute, rainwater harvesting, is physically connected with the primary water source. This generates a marginal opportunity cost of using rainwater, since harvested water does not in…ltrate. We …rst discuss the conditions that lead to a switch toward rainwater harvesting, then look at long term rainwater harvesting systems. Due to limited storage capacity, long-term use of rainwater is only possible in conjunction with groundwater. We show that this only arises if the price of water is higher than the full marginal cost of rainwater harvesting. We also provide comparative statics related to this con…guration, especially concerning the long-term water table. These results are …nally illustrated by numerical examples.
This paper studies groundwater management in the presence of rainwater harvesting (RWH). We propo... more This paper studies groundwater management in the presence of rainwater harvesting (RWH). We propose a two-state model that takes into account the standard dynamics of the aquifer and the dynamics of the storage capacity and we assume that the collection of rainwater reduces the natural recharge. We analyze the trade-o¤ between these two water harvesting techniques in an optimal control model. In particular, we show that when these techniques are pure substitutes, the development of RWH leads in the long run to a depletion of the water table even if pumping is reduced.
This paper is concerned with groundwater management issues in the presence of rainwater harvestin... more This paper is concerned with groundwater management issues in the presence of rainwater harvesting (RWH). Namely, we propose a two-state model in order to take into account the standard dynamics of the aquifer and the dynamics of the storage capacity since the collected rainwater reduces the natural recharge. We analyze the trade-off between these two water harvesting techniques in an optimal control model. We notably show that, when these techniques are pure substitutes, the development of RWH conducts in the long run to a depletion of the water table even if pumping is reduced.
This paper tackles the increasingly signicant problem of irrigation-induced soil salinity within ... more This paper tackles the increasingly signicant problem of irrigation-induced soil salinity within a groundwater management model. Irrigation can result not only in heavier salt concentrations, but also in the removal of salt from the soil through return ows. Given these contradictory observations, we are interested in the eects on soil salt concentration if irrigation eciency is improved. We develop a model of salt concentration patterns in both soil and groundwater. We introduce a negative externality to the production process by assuming that soil degradation due to higher soil salinity aects total factor productivity. Within this framework, we show that in the presence of this externality, increasing irrigation eciency can lead to higher or lower soil salt concentration, depending on the social cost of transferring salt from one reservoir to another.
This paper addresses the management of multispecies sheries, and suggests the use of restricted s... more This paper addresses the management of multispecies sheries, and suggests the use of restricted shing policies as an interesting option for unassessed sheries (as is the case within developing countries). Specically, we consider a predator-prey system where agents compete to harvest from two interacting sh species. Two management policies are considered: an unrestricted regime where agents can harvest from both species, and a second one where only the predators can be harvested. The performance of both policies is compared from an ecological and an economic point of view. For a suciently large number of agents (or for strong biological interaction parameters) the restricted shing policy is shown to yield both higher long run stock levels and prots. Thus, this contribution suggests that such a policy would require very little monitoring while meeting environmental and economic objectives.
Under what conditions can limited-tenure concessions be used to efficiently govern natural resour... more Under what conditions can limited-tenure concessions be used to efficiently govern natural resources and other public goods? We first show in a simple repeated game setting that limited tenure, with the possibility of renewal, can incentivize socially-efficient provision of public goods. We then analyze the ability of this instrument to incentivize the first best for common-pool natural resources such as fish and water, thus accounting for spatial connectivity and natural growth dynamics of the resource. The duration of tenure and the dispersal of the resource play pivotal roles in whether this limited-duration concession achieves the socially optimal outcome. Finally, in a setting with costly monitoring, we discuss the features of a concession contract that ensure first-best behavior, but at least cost to the implementing agency.
We consider analytically the non-cooperative behavior of many private property owners who each co... more We consider analytically the non-cooperative behavior of many private property owners who each controls the stock of a public bad such as an invasive weed species, infectious disease, fire, or agricultural pest. The stock of the public bad can grow and disperse across a spatial domain of arbitrary size. In this setting, we characterize the conditions under which private property owners will control or eradicate, and determine how this decision depends on property-specific environmental features and on the behavior of other landowners. We show that high mobility or lower control by others result in lower private control. But when the marginal dynamic cost of the bad is sufficiently large, we find that complete eradication may be privately optimal (despite the lack of consideration of others' welfare)in these cases, eradication arises in the non-cooperative game and is also socially optimal so there is, in effect, no externality. Finally, when property harboring the bad is not owned, or is owned in common, we derive the side payments required to efficiently control the mobile public bad.
Rainwater harvesting, consisting in collecting runo¤ from precipitation, has been widely develope... more Rainwater harvesting, consisting in collecting runo¤ from precipitation, has been widely developed to stop groundwater declines and even raise water tables. However this expected environmental e¤ect is not self-evident. We showin a simple setting that the success of this conjunctive use depends on whether the runo¤ rate is above a threshold value. Moreover, the bigger the storage capacity, the higher the runo¤ rate must be to obtain an environmentally e¢ cient system. We also extend the model to include other hydrological parameters and ecological damages, which respectively increase and decrease the environmental e¢ ciency of rainwater harvesting.
We formulate a hydro-economic model of the NorthWestern Sahara Aquifer System (NWSAS) to assess t... more We formulate a hydro-economic model of the NorthWestern Sahara Aquifer System (NWSAS) to assess the effects of intensive pumping on the groundwater stock and examine the subsequent consequences of aquifer depletion. This large system comprises multi-layer reservoirs with vertical exchanges, all exploited under open access properties. We first develop a theoretical model to account for relevant features of the NWSAS by introducing, in the standard Gisser-Sanchez model, a non-stationary demand and quadratic stock-dependent cost functions. In the second step, we calibrate parameters values using data from the NWSAS over 1955-2000. We finally simulate the time evolution of the aquifer system with exploitation under an open-access regime. We specifically examine time trajectories of the piezometric levels in the two reservoirs, the natural outlets, and the modification of water balances. We find that natural outlets of the two reservoirs might be totally dried before 2050.
Species' interactions and the involvement of shermen in several sheries may not be properly accou... more Species' interactions and the involvement of shermen in several sheries may not be properly accounted for by regulatory schemes, thus making regulation suboptimal. Being the only implementable instruments, the degree of ineciency of three second-best instruments is assessed (by using a bioeconomic multispecies model) in terms of their ability to get close to socially optimal eort and stock levels. The type of regulation and the existing biological interaction are also shown to result in dierent impacts on eort reallocation: a specic regulation does not necessarily increase the pressure on the unregulated species. Finally, we discuss how the choice of which second-best policy to implement is situation-specic.
drop of rainwater against a drop of groundwater: does rainwater harvesting really allow us to spa... more drop of rainwater against a drop of groundwater: does rainwater harvesting really allow us to spare Groundwater?
This paper studies groundwater management in the presence of rainwater harvesting (RWH). We propo... more This paper studies groundwater management in the presence of rainwater harvesting (RWH). We propose a two-state model that takes into account the standard dynamics of the aquifer and the dynamics of the storage capacity and we assume that the collection of rainwater reduces the natural recharge. We analyze the trade-o¤ between these two water harvesting techniques in an optimal control model. In particular, we show that when these techniques are pure substitutes, the development of RWH leads in the long run to a depletion of the water table even if pumping is reduced.
This paper studies a specific class of common-pool resources whereby rivalry is not characterized... more This paper studies a specific class of common-pool resources whereby rivalry is not characterized by competition for the resource stock. Artesian aquifers have been identified as a typical example, since the stock is never depleted, even when part of the resource is extracted. We first propose a dynamic model to account for relevant features of such aquifers-like water pressure, or well yield-and to characterize the corresponding dynamics. We then compare the social optimum and the private exploitation of an open-access aquifer. The comparison of these two equilibria allows us to highlight the existence of a new source of inefficiency. We refer to this as pressure externality. This externality results in the long run in an additional number of wells for the same water consumption, and hence additional costs. Finally, we characterize a specific stock-depend tax to neutralize the pressure externality. JEL Classification: H21, H23, Q15, Q25, C61
Species' interactions and the involvement of fishermen in several fisheries may not be proper... more Species' interactions and the involvement of fishermen in several fisheries may not be properly accounted for by regulatory schemes,thus making regulation suboptimal. Being the only implementable instruments, the degree of ineffciency of three second-best instruments is assessed (by using a bioeconomic multispecies model) in terms of their ability to get close to socially optimal effort and stock levels. The type of regulation and the existing biological interaction are also shown to result in different impacts on effort re-allocation: a specific regulation does not necessarily increase the pressure on the unregulated species. Finally, we discuss how the choice of which second-best policy to implement is situation-specific.
For a few decades, a growing literature has examined the role of water resources in interstate co... more For a few decades, a growing literature has examined the role of water resources in interstate con icts. In line with this literature, this study analyzes the risk of a con ict between countries sharing freshwater. While some scholars claim that waterbased con icts can never occur, this analysis determines this risk by linking it to the size of a negotiation interval; the probability-to-con ict decreasing with this size. In fact, we are going to show that the size of this interval diminishes with scarcer resources and with the degree of the heterogeneity of countries measured by their productive e ciency. Then, in a peace scenario, we determine by bargaining the optimal allocation and we study its variation according to the parameters of the model. These theoretical results will be con rmed by an econometric approach.
This paper is concerned with discrete choice contingent value estimate when the respondents are u... more This paper is concerned with discrete choice contingent value estimate when the respondents are uncertain about the environmental amenities. Within a class of indirect utility functions often used in empirical studies, the authors put forwards the effect of the risk premium on the willingness to pay (WTP). Then, it is shown how this risk premium also modi es the estimation procedure. A Monte Carlo simulation concludes the paper by putting forward a misestimation of the WTP. When this uncertainty is ignored, more precisely, the authors focus on the effect of the risk premium.
We examine theoretically a system of spatial property rights over a mobile re- newable resource. ... more We examine theoretically a system of spatial property rights over a mobile re- newable resource. The resource grows and is harvested in each area, but harvest in one patch imposes an externality on other patches through resource movement. This externality gives rise to over-extraction by non-cooperative patch owners. We propose a new institutional arrangement to internalize this externality. The in- strument involves granting limited-duration tenure, with the possibility of renewal, to each of the N interconnected concessionaries. Renewal of concession i is predi- cated on concessionaire i having never driven the stock below a pre-defined target Si. We show that not only can this instrument improve upon the decentralized property right solution, but under general conditions it can replicate the socially optimal extraction in every patch and every time period, in perpetuity. The dura- tion of tenure and the dispersal of the resource play pivotal roles in whether this instrument achie...
However, the economic rationale for groundwater management has been widely questioned since the s... more However, the economic rationale for groundwater management has been widely questioned since the seminal work of Gisser and Sánchez on the small benefits from regulation. Competitive extraction occurs where there is no regulation, i.e. where a limited number of groundwater users privately exploit the resource and each individual user ignores the impact of her pumping on others and on the overall state of the resource. Sometimes this is referred to as the “free-market scenario”. Optimal extraction refers to an optimal control scenario where a social planner maximizes the social welfare for all users. Many studies have argued that there may be no significant difference between competitive and optimal pumping rates. This result is now known as the Gisser-Sánchez Effect (GSE).
We consider groundwater managed by a sole owner and where a perfect substitute, rainwater harvest... more We consider groundwater managed by a sole owner and where a perfect substitute, rainwater harvesting, is physically connected with the primary water source. This generates a marginal opportunity cost of using rainwater, since harvested water does not in…ltrate. We …rst discuss the conditions that lead to a switch toward rainwater harvesting, then look at long term rainwater harvesting systems. Due to limited storage capacity, long-term use of rainwater is only possible in conjunction with groundwater. We show that this only arises if the price of water is higher than the full marginal cost of rainwater harvesting. We also provide comparative statics related to this con…guration, especially concerning the long-term water table. These results are …nally illustrated by numerical examples.
This paper studies groundwater management in the presence of rainwater harvesting (RWH). We propo... more This paper studies groundwater management in the presence of rainwater harvesting (RWH). We propose a two-state model that takes into account the standard dynamics of the aquifer and the dynamics of the storage capacity and we assume that the collection of rainwater reduces the natural recharge. We analyze the trade-o¤ between these two water harvesting techniques in an optimal control model. In particular, we show that when these techniques are pure substitutes, the development of RWH leads in the long run to a depletion of the water table even if pumping is reduced.
This paper is concerned with groundwater management issues in the presence of rainwater harvestin... more This paper is concerned with groundwater management issues in the presence of rainwater harvesting (RWH). Namely, we propose a two-state model in order to take into account the standard dynamics of the aquifer and the dynamics of the storage capacity since the collected rainwater reduces the natural recharge. We analyze the trade-off between these two water harvesting techniques in an optimal control model. We notably show that, when these techniques are pure substitutes, the development of RWH conducts in the long run to a depletion of the water table even if pumping is reduced.
This paper tackles the increasingly signicant problem of irrigation-induced soil salinity within ... more This paper tackles the increasingly signicant problem of irrigation-induced soil salinity within a groundwater management model. Irrigation can result not only in heavier salt concentrations, but also in the removal of salt from the soil through return ows. Given these contradictory observations, we are interested in the eects on soil salt concentration if irrigation eciency is improved. We develop a model of salt concentration patterns in both soil and groundwater. We introduce a negative externality to the production process by assuming that soil degradation due to higher soil salinity aects total factor productivity. Within this framework, we show that in the presence of this externality, increasing irrigation eciency can lead to higher or lower soil salt concentration, depending on the social cost of transferring salt from one reservoir to another.
This paper addresses the management of multispecies sheries, and suggests the use of restricted s... more This paper addresses the management of multispecies sheries, and suggests the use of restricted shing policies as an interesting option for unassessed sheries (as is the case within developing countries). Specically, we consider a predator-prey system where agents compete to harvest from two interacting sh species. Two management policies are considered: an unrestricted regime where agents can harvest from both species, and a second one where only the predators can be harvested. The performance of both policies is compared from an ecological and an economic point of view. For a suciently large number of agents (or for strong biological interaction parameters) the restricted shing policy is shown to yield both higher long run stock levels and prots. Thus, this contribution suggests that such a policy would require very little monitoring while meeting environmental and economic objectives.
Under what conditions can limited-tenure concessions be used to efficiently govern natural resour... more Under what conditions can limited-tenure concessions be used to efficiently govern natural resources and other public goods? We first show in a simple repeated game setting that limited tenure, with the possibility of renewal, can incentivize socially-efficient provision of public goods. We then analyze the ability of this instrument to incentivize the first best for common-pool natural resources such as fish and water, thus accounting for spatial connectivity and natural growth dynamics of the resource. The duration of tenure and the dispersal of the resource play pivotal roles in whether this limited-duration concession achieves the socially optimal outcome. Finally, in a setting with costly monitoring, we discuss the features of a concession contract that ensure first-best behavior, but at least cost to the implementing agency.
We consider analytically the non-cooperative behavior of many private property owners who each co... more We consider analytically the non-cooperative behavior of many private property owners who each controls the stock of a public bad such as an invasive weed species, infectious disease, fire, or agricultural pest. The stock of the public bad can grow and disperse across a spatial domain of arbitrary size. In this setting, we characterize the conditions under which private property owners will control or eradicate, and determine how this decision depends on property-specific environmental features and on the behavior of other landowners. We show that high mobility or lower control by others result in lower private control. But when the marginal dynamic cost of the bad is sufficiently large, we find that complete eradication may be privately optimal (despite the lack of consideration of others' welfare)in these cases, eradication arises in the non-cooperative game and is also socially optimal so there is, in effect, no externality. Finally, when property harboring the bad is not owned, or is owned in common, we derive the side payments required to efficiently control the mobile public bad.
Rainwater harvesting, consisting in collecting runo¤ from precipitation, has been widely develope... more Rainwater harvesting, consisting in collecting runo¤ from precipitation, has been widely developed to stop groundwater declines and even raise water tables. However this expected environmental e¤ect is not self-evident. We showin a simple setting that the success of this conjunctive use depends on whether the runo¤ rate is above a threshold value. Moreover, the bigger the storage capacity, the higher the runo¤ rate must be to obtain an environmentally e¢ cient system. We also extend the model to include other hydrological parameters and ecological damages, which respectively increase and decrease the environmental e¢ ciency of rainwater harvesting.
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Papers by agnes tomini