Extensive Groundwater Withdrawals Research Articles

“You turn the tap on, the water's there, and you just think everything's fine”: a mixed methods approach to understanding public perceptions of groundwater management in Baton Rouge, Louisiana, USA

In Louisiana's Capital Area Groundwater Conservation District (CAGWCD), extensive groundwater withdrawals from the Southern Hills Aquifer System have begun to accelerate the infiltration of saltwater into the aquifer's freshwater sands. This accelerated saltwater intrusion has the potential to reduce the amount of groundwater available for public consumption and other industrial and agricultural uses throughout the region. In response to this threat, the Capital Area Ground Water Conservation Commission has begun development of a long-term strategic plan to achieve and maintain sustainable and resilient groundwater withdrawals from the aquifer system. The development of the strategic plan includes an assessment of public attitudes regarding groundwater and groundwater management in the CAGWCD. This paper presents the results of mixed methods public participatory research to evaluate current and historical views and attitudes around groundwater quality, quantity, and cost in the CAGWCD. The mixed methods approach used in this research employed a sequential explanatory design model consisting of two phases. The first phase involved the implementation of an internet-based survey, followed by a qualitative phase aimed at explaining and enhancing the quantitative results. The qualitative phase employed a combination of one-on-one interviews and focus groups. The research found that the primary governance obstacle that decision-makers may face in managing groundwater is a broad lack of public awareness of groundwater and groundwater issues in the CAGWCD. Despite the criticality of over-pumping and saltwater intrusion into the aquifer system, survey research and subsequent interviews and focus groups have shown that the public is largely unaware of these issues. This research also found a general lack of trust in both industry and government to manage groundwater issues and highlighted the need for groundwater management efforts to be led by unbiased, trusted institutions.

Increases in groundwater arsenic concentrations and risk under decadal groundwater withdrawal in the lower reaches of the Yellow River basin, Henan Province, China

The spatiotemporal variability in groundwater arsenic concentrations following extensive groundwater extractions over decades was rarely studied on a large scale. To fill this gap, variations in groundwater arsenic concentrations in the North Henan Plain in China from 2010 to 2020 were investigated. The possibility of high-arsenic groundwater (>10 μg/L) was higher than 40% in aquifers within a distance of 100 m from paleochannels. This may be due to the fact that deposits in paleochannels were rich in organic matter and suitable for arsenic enrichment. Following groundwater withdrawal over ten years from 2010 to 2020, nearly half of groundwater samples (44%) were elevated in groundwater arsenic concentrations, and the proportion of high arsenic groundwater increased from 24% in 2010 to 26% in 2020. These may be related to enhanced Fe(III) oxide reduction under decadal groundwater withdrawal. However, around 56% groundwater samples were decreases in arsenic concentrations because of increased NO3− levels in these samples in 2020. Furthermore, extensive groundwater withdrawal decreased groundwater tables averagely by 4.6 m from 2010 to 2020, which induced the intrusion of high-arsenic groundwater from shallow aquifers into deeper ones. More importantly, the long-term groundwater pumping has perturbed groundwater flow dynamics and redistributed high-arsenic groundwater in the plain, leading to 18% more areas and 33.8% more residents being potentially at risk. This study suggests that the threat of groundwater overexploitation may be much more severe than previously expected.

Land Subsidence and Its Relations with Sinkhole Activity in Karapınar Region, Turkey: A Multi-Sensor InSAR Time Series Study.

The Karapinar basin, located in the Central Anatolian part of Turkey, is subjected to land subsidence and sinkhole activity due to extensive groundwater withdrawal that began in the early 2000s. In this study, we use Interferometric Synthetic Aperture Radar (InSAR), Global Navigation Satellite System (GNSS), and groundwater level data to monitor and better understand the relations between groundwater extraction, land subsidence, and sinkhole formation in the Karapinar basin. The main observations used in the study are InSAR-derived subsidence velocity maps calculated from both Sentinel-1 (2014–2018) and COSMO-SkyMed (2016–2017) SAR data. Our analysis reveals broad areas of subsidence with rates exceeding 70 mm/yr. The InSAR-derived subsidence was compared with GNSS data acquired by a continuously operating GNSS station located in the study area, which show a similar rate of subsidence. The temporal characteristic of both InSAR and GNSS time series indicate a long-term subsidence signal superimposed by seasonal variability, which follows the overall groundwater level changes, with over 80% cross-correlation consistency. Our results also indicate that sinkhole activity is limited to slow subsidence areas, reflecting strong cohesion of near-surface rock layers that resist subsidence but yield to collapse in response to aquifer system deformation induced by groundwater extraction.

Land subsidence caused by groundwater exploitation in Quetta and surrounding region, Pakistan

Abstract. Land subsidence is effecting several metropolis in the developing as well as developed countries around the world such as Nagoya (Japan), Shanghai (China), Venice (Italy) and San Joaquin valley (United States). This phenomenon is attributed to natural as well as anthropogenic activities that include extensive groundwater withdrawals. Quetta which is facing similar subsidence phenomenon is the largest city of Balochistan province in Pakistan. This valley is mostly dry and ground water is the major source for domestic and agricultural consumption. The unplanned use of ground water resources has led to the deterioration of water quality and quantity in the Quetta valley. Water shortages in the region was further aggravated by the drought during (1998–2004) that affected the area forcing people to migrate from rural to urban areas. Refugees from the war torn neighboring Afghanistan also contributed to rapid increase in population of Quetta valley that has increased from 0.26 million in 1975 to 3.0 million in 2016. The objective of this study was to measure the land subsidence in Quetta valley and identify the effects of groundwater withdrawals on land subsidence. To achieve this goal, data from five Global Positioning System (GPS) stations in Quetta were acquired and processed. Furthermore the groundwater decline data from 41 observation wells during 2010 to 2015 were calculated and compared with the land deformation. The results of the GPS readings revealed that the land of Quetta valley is subsiding from 30 mm yr−1 on the flanks to 120 mm yr−1 in the central part. 1.5–5.0 m yr−1 of groundwater level drop was recorded in the area where the rate of subsidence is highest. Whereas 9–10 cm of subsidence was recorded in the surrounding areas of Quetta where agriculture and settlements are high. The surrounding areas include Kuchlak, Mastung, Pishin, Gulistan and Hurumzai districts. These results were acquired using InSAR imagery collected from October 2014 to march 2019. So the extensive groundwater withdrawals in Quetta valley and surrounding areas is considered to be the driving force behind land subsidence.

Reconstruction of earth fissures 3-D from videos

Abstract. Earth fissures are pervasive cracks that develop on valley floors as a consequence of land subsidence associated with extensive groundwater withdrawal. To capture geometrical, geological and geotechnical information of ground fissures is of paramount importance for their characterization. Recent advances in remote sensing techniques and the accessibility to remotely piloted aircraft systems (RPAS) as well as the evolution of onboard digital cameras enable the capture of digital photos and videos. Using digital photos along with the Structure from Motion (SfM) technique and following certain strategies, we can reconstruct a 3-D model of the earth fissures under study. This technique requires digital photos, but when a digital video is available, we can convert it into a set of frames and equally apply the procedure. Besides, the extraction of frames from a video assures a key condition for the SfM technique: the overlap between photos. The resulting 3-D model should be scaled and oriented using a rigid transformation matrix or even better including ground control points (GCP) into the captured photos or frames. The latter enables the geo-referencing of the point cloud and the correction of linear and non-linear deformations. In this work, the proposed methodology is illustrated through the application of SfM technique to a high-resolution video downloaded from YouTube (i.e. https://youtu.be/9xdAnftBKvY, last access: 20 February 2020). The video shows a mile-long earth fissure that appeared sometime between March 2014 and December 2014 near the Tator Hills (Arizona, USA) over Quaternary sediments. The Arizona Geological Survey captured these videos using an RPAS. The frames of the video were downloaded and extracted using a simple Matlab code. Then, we sub-sampled the frames and processed them using the software Agisoft Metashape Professional. Finally, we got metric data from Google Earth and generated a 3-D model. The quality of the 3-D model strongly depends on the quality of the photos and the GCP. However, this study shows the potential of this technique, instrumentation and data available on Internet for the development of 3-D point clouds and 3-D models for the detailed analysis of earth fissures.

Understanding the dynamic behaviour for the Madrid aquifer (Spain): insights from the integration of A-DInSAR and 3-D groundwater flow and geomechanical models

Abstract. Advanced Differential Interferometric Synthetic Aperture Radar (A-DInSAR) techniques and 3-D groundwater flow and geomechanical models are integrated to improve our knowledge about the Tertiary detritic aquifer of Madrid (TDAM). In particular, the attention is focused on the Manzanares-Jarama well field, located to the northwest of Madrid, which experienced five cycles of extensive groundwater withdrawal followed by natural recovery, to cope with the droughts occurred in summer 1995, 1999, 2002, 2006, and 2009. Piezometric records and A-DInSAR data acquired by ERS-1/2 and ENVISAT satellites during the periods 1992–2000 and 2002–2010, respectively, have been used to calibrate the groundwater flow and the geomechanical models. A time-lag of about one month between the hydraulic head changes and the displacements of the land surface has been detected by a joint wavelet analysis of A-DInSAR and piezometer head time series. Overall, the results show the effectiveness of the proposed integrated approach composed of A-DInSAR and 3-D geomechanical model to characterize the aquifer-system response during and after the groundwater withdrawal.

Investigation of Land Subsidence Based on the Column Element Settlement Model in a Soft-Soil Area

The Su-Xi-Chang area is located in the Yangtze River Delta in southeastern Jiangsu Province, China. More than 2 m cumulative land subsidence has occurred since 1980s. A range of monitoring programs, geological investigations, and numerical modeling has been implemented in order to establish a regional rehabilitation plan. In this paper, the column element settlement model (CESM) has been established to investigate the coupling effect of soil self-weight, upper loads, and groundwater withdrawal on land subsidence. The model has been verified by comparing with the land subsidence records in Changzhou and further applied to the investigation area. The results show that extensive groundwater withdrawal is the main cause of the land subsidence. Settlement caused by soil self-weight increases with the depth and decreases with upper loads, while settlement caused by upper loads increases with the intensity of upper loads and decreases with depth. The proportion of ground settlement caused by soil self-weight, upper loads, and groundwater withdrawal is also investigated.

Water Security for Agriculture: Introduction to the Water Security Task Force Symposium

Published in Agron. J. 107:1524–1525 (2015) doi:10.2134/agronj15.0909 Available freely online through the author-supported open access option. Copyright © 2015 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. F.F. Vocasek, Servi-Tech Laboratories, Dodge City, KS 67801; G.A. Peterson (retired), Soil and Crop Sciences Dep., 301 University Ave., Colorado State Univ., Ft. Collins, CO 80523. Received 5 May 2015. Accepted 5 May 2015. *Corresponding author (Gary.Peterson@ colostate.edu). The American Society of Agronomy (ASA) created the Water Security for Agriculture Task Force at its annual meeting in San Antonio, TX, in 2011. The “Task Force” was proposed by the ASA Science Policy Committee as follows:

Land subsidence and declining water resources in Quetta Valley, Pakistan

Extensive groundwater withdrawals in urban areas may cause water shortages, land subsidence, and water quality problems. The Quetta Valley is the largest population center in Balochistan province in western Pakistan. This area is arid and groundwater is the main water source for domestic and agricultural use. This work presents global positioning system (GPS) data and assessment of spatial and temporal variations in water levels. GPS data from two stations from mid-2006 to the beginning of 2009 show subsidence rate of 10 cm\year. Nine satellite images from 1975 to 2009 were classified and processed to quantify land cover and land use changes, which highlight an increase in agricultural areas in the central region of the Quetta Valley, as well as reduced vegetation on mountains. These data correspond to gradual temporal changes in water volumes in streams and lakes. Average temperatures have also increased and mean precipitation has decreased during this period. However, the greatest change in this area has been in population growth, which rose from 260,000 in 1975 to 1.2 million in 2010, mainly due to migration of refugees from war-torn neighboring Afghanistan. The Quetta Valley provides a good example for studying the impact of urbanization on water resources.

Influences of groundwater extraction on the distribution of dissolved As in shallow aquifers of West Bengal, India

Here we report temporal changes of As concentrations in shallow groundwater of the Bengal Delta Plain (BDP). Observed fluctuations are primarily induced by seasonally occurring groundwater movement, but can also be connected to anthropogenic groundwater extraction. Between December 2009 and July 2010, pronounced variations in the groundwater hydrochemistry were recorded in groundwater samples of a shallow monitoring well tapping the aquifer in 22–25m depth, where Astot concentrations increased within weeks from 100 to 315μgL−1. These trends are attributed to a vertically shift of the hydrochemically stratified water column at the beginning of the monsoon season. This naturally occurring effect can be additionally superimposed by groundwater extraction, as demonstrated on a local scale by an in situ experiment simulating extensive groundwater withdrawal during the dry post-monsoon season. Results of this experiment suggest that groundwater extraction promoted an enduring change within the distribution of dissolved As in the local aquifer. Presented outcomes contribute to the discussion of anthropogenic pumping influences that endanger the limited and yet arsenic-free groundwater resources of the BDP.

Aquifer heterogeneity and response time: the challenge for groundwater management

Groundwater is an important contributor to irrigation water supplies. The time lag between withdrawal and the subsequent impacts on the river corridor presents a challenge for water management. We highlight aspects of this challenge by examining trends in the groundwater levels and changes in groundwater management goals for the Namoi Catchment, which is within the Murray–Darling Basin, Australia. The first high-volume irrigation bore was installed in the cotton-growing districts in the Namoi Catchment in 1966. The development of high-yielding bores made accessible a vast new water supply, enabling cotton growers to buffer the droughts. Prior to the development of a groundwater resource it is difficult to accurately predict how the water at the point of withdrawal is hydraulically connected to recharge zones and nearby surface-water features. This is due to the heterogeneity of the sediments from which the water is withdrawn. It can take years or decades for the impact of groundwater withdrawal to be transmitted kilometres through the aquifer system. We present the analysis of both historical and new groundwater level and streamflow data to quantify the impacts of extensive groundwater withdrawals on the watertable, hydraulic gradients within the semi-confined aquifers, and the movement of water between rivers and aquifers. The results highlight the need to monitor the impacts of irrigated agriculture at both the regional and local scales, and the need for additional research on how to optimise the conjunctive use of both surface-water and groundwater to sustain irrigated agriculture while minimising the impact on groundwater-dependent ecosystems.

Prediction of Land Subsidence Under Cyclic Pumping Based on Laboratory and Numerical Simulations

In this study subsidence due to groundwater withdrawal was investigated. Kerman Province in Iran is struggling with land subsidence problem due to extensive groundwater withdrawal mainly for farming. The rate and type of groundwater withdrawal has very important impact on settlement rate. In this research, effective parameters on land subsidence caused by groundwater withdrawal were determined by laboratory tests. Sampling had done up to depth of 300 m mainly with remolded specimens from Shams-abad, Nouq plain in Kerman province. Similar to the field preconsolidation pressure was applied on specimens in the laboratory. Rate of applied stress on prepared specimens was similar to effect of oscillation of groundwater level. In order to model the actual soil behavior in the laboratory, one-dimensional consolidation device (odometer) was adopted for testing. In these tests, the effect of loading caused by seasonal oscillation of groundwater table is considered by means of cyclic loading in the testing which has great effect on rate of settlements. The results of tests show that when the water table level periodically increases and decreases the amount of settlement decrease, comparing with the case when the groundwater table drop to a constant level. In order to predict the further effects of groundwater level oscillation and actual field condition on land subsidence, a finite element model based on Biots’ three-dimensional consolidation theory was developed. After calibration of finite element model with laboratory tests, this model was used for prediction the effect of groundwater level oscillation on actual field conditions.

Soil salinization in the agricultural lands of Rhodope District, northeastern Greece

The objective of this study was to identify seasonal and spatial trends and soil salinization patterns in a part of Rhodope District irrigated land, northeastern Greece, located east of Vistonis Lagoon. The study area is irrigated from a coastal aquifer, where salt water intrusion occurs because of extensive groundwater withdrawals. Fourteen monitoring sites were established in harvest fields in the study area, where soil samples were collected. Electrical conductivity (ECe), pH, and ion concentrations were determined in the saturated paste extract of the soil samples in the laboratory using standard methods. A clear tendency was observed for ECe to increase from April to September, i.e., within the irrigation period, indicating the effect of saline groundwater to soil. In the last years, the change from moderately sensitive (e.g., corn) to moderately tolerant crops (e.g., cotton) in the south part of the study area indicates the impacts of soil salinity. The study proposes management methods to alleviate this problem.

Effects of human activities and urbanization on groundwater environments: An example from the aquifer system of Tokyo and the surrounding area

The Kanto plain that is the largest depositional plain in Japan has the largest urbanized area called Tokyo Metropolitan Area. This plain has experienced extensive groundwater withdrawals for water resources and human induced disasters such as land subsidence in the process of urbanization. Japanese national government and local governments have monitored groundwater levels and settlement of ground surface for about half a century. These data are useful not only for the prevention of these disasters but for the evaluation of the change of groundwater flow beneath the urbanized area. However, few hydrological and hydrogeological studies about the change of groundwater flow in this plain have been conducted until now except for several studies which were limited in areal extent. In this paper, changes of the distribution of hydraulic heads in the central part of this plain are discussed using the long-term groundwater level observation data to evaluate the change of groundwater flow. The temporal changes in the distribution of hydraulic heads in a major confined aquifer (the second aquifer) and the areal extent of the urbanized area for approximately 50 years can be summarized as follows. In the latter half of the 1950s, urban area was limited in the southern region of the study area and hydraulic head gradually declined from the northwest to the southeast in the study area. After the 1960s, urban area extended toward the north and groundwater in the northern part was largely abstracted until the 1980s. As a result, hydraulic heads in this area markedly declined. On the other hand, hydraulic heads in the southern part began to rise because of the restriction of groundwater withdrawals. In recent years, low hydraulic head area has been formed from the northern region to the central region. These results suggest that the groundwater flow which was affected by urbanization (groundwater withdrawals) has continued to change over several decades, even after the regulation of withdrawals, and hence, the continued monitoring of the groundwater environment is important for the sustainable use of groundwater resources.

Origin of shallow ground water in an alluvial aquifer as determined by isotopic and chemical procedures.

In this study, we identify the origin of shallow ground water that supports regionally unique plant and wildlife habitats in a riparian and reservoir-fringe system using isotopic and chemical procedures. This study was conducted where Little Stony Creek flows into East Park Reservoir on the east front of the Coast Range, northern California. Little Stony Creek water, Hyphus Creek water, Franciscan Complex regional ground water, Great Valley Group regional ground water, and local shallow ground water were collected during wet and dry seasons and were analyzed for deuterium, oxygen-18, temperature, pH, redox potential, conductivity, and major cation and anion concentrations. Turnover in the local flow system is rapid indicating that local shallow ground water is dependent on recent recharge. Local shallow ground water is recharged primarily by Little Stony Creek water and Franciscan Complex ground water. In the wet season, Little Stony Creek is the more prominent source of local shallow ground water, and the ratio of Little Stony Creek water to Franciscan Complex ground water decreases with distance from the channel. In the dry season, Franciscan Complex ground water is the more prominent source of local shallow ground water, and the ratio of Little Stony Creek water to Franciscan Complex ground water decreases with distance down the valley. Franciscan Complex ground water discharges to local shallow ground water throughout the year, primarily because the local flow system is a regional low that lies perpendicular to the Franciscan Complex ground water flowpath. Little Stony Creek is a more prominent source of ground water in the wet season than in the dry season because Little Stony Creek flows continuously through the alluvial reach in the wet season and intermittently through the alluvial reach in the dry season. Extensive ground water withdrawals from the Franciscan Complex flow system could reduce the amount of water available to the local flow system, particularly during the dry season, and could substantially reduce the geographic extent of the regionally unique plant and wildlife habitats.

Mathematical Simulation of the Subsidence of Ravenna

Land subsidence at Ravenna is the result of aquitard and reservoir compaction caused, respectively, by extensive groundwater withdrawals from the unconsolidated Quaternary basin and gas production from a number of pre‐Quaternary pools scattered over the area. Water pumpage paralleled the postwar industrial development of Ravenna until the middle seventies when consumption was drastically curtailed owing to the economic crisis and the activation of a new aqueduct. Gas production started in 1952. The exploitation of several reservoirs is currently under way and the search for new fields is still in progress. Geodetic records indicate that the maximum cumulative subsidence over the period 1950–1986, including a natural geologic settlement of perhaps 2 mm/yr, has been 1.30 m in the industrial zone of Ravenna. In 1980 the municipality promoted a reconnaissance study with the primary aim of providing the information base needed to reconstruct the actual occurrence, understand correctly the physical behavior and produce the essential input data to a mathematical model which realistically relates the subsidence of the city to groundwater withdrawal and gas removal with an emphasis on their respective influences. The results from the three‐dimensional numerical simulations, performed with the aid of mixed finite element, finite difference and integral models, show that the primary responsibility for the regional land sinking should be placed on the subsurface water overdraft which occurred until the middle 1970s. Gas withdrawal plays a role restricted to the area overlying each reservoir with a magnitude depending on the depth of burial, thickness of mineralized rocks and overall volumetric production. A major environmental impact may be expected where the gas subsidence bowl is intersected by the Adriatic coastline.

The Belchatow, Poland, earthquakes of 1979 and 1980 induced by surface mining

Five seismic events occurred between August 1979 and May 1980 in the Belchatow trench area in central Poland, where large brown-coal deposits have been surface-mined since 1976. The three largest shocks had a local magnitude M L = 3.5 , seismic moment M o = 1.5 · 10 14 N-m and source radius r = 350m , approximately. The tremors had maximum intensity between 5 and 6, and from the magnitude—intensity—depth relation, the focal depth was estimated to be between 1 and 5 km. The Belchatow tremors are the manifestation of an unusual type of induced seismicity, i.e., seismicity connected with surface mining. The removal of overburden and extensive ground-water withdrawal by the mining operations seem to be direct factors responsible for stress concentration, although preexisting tectonic stress might be the most important indirect factor responsible for the origin of these events.

Active faults in southeastern Harris county, texas

A complex graben southeast of Houston, Texas, extends eastwest across the Friendswood-Webster oil field and Interstate Highway 45, through Ellington Air Force Base (EAFB), northeastward through a new residential subdivision, into the Clear Lake oil field, and on to LaPorte, Texas. Some of the faults in this graben system are known to have been active for decades and are represented by scarps several meters high in the deltaic deposits of the Pleistocene Beaumont formation. In the protected environment under two of the buildings at EAFB, one of the faults in this graben occurs as a sinuous fissure 8 to 10 cm wide that is open to a depth of about 35 cm. Another fault system appears to control the shoreline configuration of Clear Lake and the courses of streams tributary to the lake. Rapid urbanization of the surrounding area began in 1962 and damage to buildings and pavements along certain faults in this system became evident about 1970. Although some of the faults are associated with tectonic movements and the production of oil and gas, many of the faults appears to be related to extensive ground-water withdrawal and the consequent dewatering and compaction of the sands and clays in the aquifer.

Mathematical simulation of the subsidence of Venice: 2. Results

Land subsidence at Venice is the result of aquitard compaction caused by extensive groundwater withdrawals from the unconsolidated Quaternary aquifer‐aquitard system that underlies the Venetian lagoon. A two‐step mathematical model consisting of a regional hydrologic model and a local subsidence model has been used to analyze the system. Results show that the total subsidence over the period 1930–1973 has been about 15 cm. Geodetic records, which cover only the latter portion of this period, provide documentary evidence for a 10‐cm subsidence during 1952–1969. Simulations of the past used to calibrate the model show that extractions from a single large well in the Tronchetto region of Venice have exerted a small but measurable influence on the subsidence, but the main responsibility for subsidence at Venice must be placed on the heavy industrial pumpage at the mainland port of Marghera. Predictive simulations show that any changes in the withdrawal rate at Marghera will tend to propagate their effects to Venice in a relatively short time, and there will be little delay between the occurrence of head declines at Venice and the resulting subsidence. If withdrawals at Tronchetto and Marghera are kept constant in the future as they have been since 1969, about 3 cm of further subsidence can be expected. Subsidence could be arrested at its present level by a shutdown of the Tronchetto well and a reduction of Marghera pumpage to three quarters of its present value. Complete cessation of all pumping would provide a modest rebound of about 2 cm over the next 25 years. The results of this study are based on a model that was limited by the requirements of radial symmetry and a calibration that was hampered by the sparseness of the available data. The subsidence situation at Venice should remain under continued evaluation as further data become available and more complex models become feasible.

Predictive Simulation of the Subsidence of Venice

Land subsidence at Venice is the result of sediment compaction in the unconsolidated, aquifer-aquitard system that underlies the Venetian Lagoon. Compaction is caused by extensive groundwater withdrawals at the nearby industrial port of Marghera. The total subsidence at Venice for the period from 1930 through 1973 has been about 15 centimeters. Predictive simulations with a calibrated mathematical model were hampered by the sparseness of available data, but, as a first estimate, they suggest that, if withdrawals are kept constant in the future as they have been since 1969, about 3 centimeters of further subsidence can be expected.