Modelling a fractured aquifer: what can be learned by the Mulino delle Vene springs (northern Apennines)?

Dimensione: px

Iniziare la visualizzazioe della pagina:

Download "Modelling a fractured aquifer: what can be learned by the Mulino delle Vene springs (northern Apennines)?"

Rosina Emma Castelli
8 anni fa
Visualizzazioni

$Modelling a fractured aquifer: what can be learned by the Mulino delle$ Errigo 2, F. Cervi 1.

1 Modelling a fractured aquifer: what can be learned by the Mulino delle Vene springs (northern Apennines)? F. Petronici 1, L. Borgatti 1, D. Errigo 2, F. Cervi 1. 1 DICAM - Dipartimento di Ingegneria Civile, Chimica, Ambientale e dei Materiali - Università di Bologna 2 ARPA Emilia-Romagna

2 Introduction Numerical model Steady state simulation Calibration Transient simulation Validation

$First results of the numerical modelling and advancements in the understanding of fractured$

3 WHERE: Mulino delle Vene springs, Carpineti, Reggio Emilia Province, northern Apennines. ACTIVITY: Hydrogeological modelling of a non-porous aquifer. GOALS: Water resources analysis. First results of the numerical modelling and advancements in the understanding of fractured aquifers. Tresinaro River, Mulino delle Vene (Carpineti, RE). Croveglia s pool (Carpineti,RE).

$First results of the numerical modelling and advancements in the understanding of fractured$

4 Why Mulino delle Vene? Despite the wide outcropping of rocky aquifers in the mountainous sectors of Italy, mathematical approaches for simulating their hydrological behavior have not been exploited extensively to date. This is mainly due to: 1. Heterogeneity of the hydrogeological properties characterizing the fractured aquifers; 2. Scarcity of continuous monitoring data. Continuous monitoring of discharge Mulino delle Vene Geological data Pumping tests Groundwater level monitoring PECULIAR CASE STUDY

$Heterogeneity of the hydrogeological properties characterizing the fractured aquifers; 2.$

The bedding of the slab is gently dipping towards the southeast (where the springs are located).

5 Geological data The springs originate at the bottom of a 50 m long slope. This slope is the southern termination of a continuous and poorly-deformed arenite slab (PAT4) that overlay almost impermeable marls (CTG). The bedding of the slab is gently dipping towards the southeast (where the springs are located). A Geological map and cross-section AA, Carpineti, Reggio Emilia Province. A A A 1:40000 LEGEND: PAT4 Santa Maria Formation, arenitic units. PAT Pantano Formation, arenitic units. CTG Contignaco Formation, marly units. CIG Cigarello Formation, arenitic units. Cross-section. Mulino delle Vene springs, 420 m a.s.l.

6 Recharge area Hydrogeological analysis (pumping tests and estimation of permeability from geomechanical surveys) allowed to define the recharge area of Mulino delle Vene springs. Extension of 5,5 km 2. Average elevation of 580 m a.s.l. All the water coming from the springs then flows into the Tresinaro River, few meter downslope. Wells RMR Study area, Carpineti, Reggio Emilia Province.

7 Hydrological and discharge data 1) Effective daily rainfall (R) (corrected with Penman-Monteith formula and Corine Land Cover data) from 15 th March 2013 to 31 st October 2013; 2) Continuous discharge (Q) from Mulino delle Vene springs (15 th March 2013 to 31 st October 2013), linked to the discharge from the weir equipped with an electric-transducer (acquisition time set at 1 hour) with a curvilinear regression Q (m 3 d -1 ) R (mmd -1 ) Weir and electric transducer, Mulino delle Vene, 430 m a.s.l Mar-13 May-13 Jul-13 Aug-13 Oct-13 time 0 Effective rainfall Discharge

equipped with an electric-transducer (acquisition time set at 1 hour) with a curvilinear regression.

Numerical model Geometry: Top slice: Digital Elevation Model; Bottom slice: 8 geological sections; Boundary of the recharge area defined by a geomorphological and hydrogeological

8 Numerical model Geometry: Top slice: Digital Elevation Model; Bottom slice: 8 geological sections; Boundary of the recharge area defined by a geomorphological and hydrogeological analysis. Elevation (m a.s.l.) Equivalent Porous Medium (EPM) approach MESH PROPERTY: 7395 nodes; 9442 triangle elements; dimension of m. Mulino delle Vene springs Seepage face condition

analysis. Elevation (m a.s.l.) Equivalent Porous Medium (EPM) approach MESH PROPERTY: 7395

9 Steady state simulation Goals: Hydrogeological balance (P=Q); One layer model Dynamic storage ~ 1,6 Mm 3 ; Fitting groundwater level in wells. ok Two layers model Parameters k (ms -1 ) s Layer 1 6x10-5 0,01 Layer 2 1x10-7 0,001 k: permeabilty; s: storativity. Elevation (m a.s.l.) Hydraulic head (m a.s.l.) Q Water surface.

ok Two layers model Parameters k (ms -1 ) s Layer 1 6x10-5 0,01 Layer 2 1x10-7

Calibration parameters: permeability (k) and storativity (s) of the first layer.

10 Calibration - Transient simulation Calibration period: from June to August 2013, without rainfall recharge. Calibration parameters: permeability (k) and storativity (s) of the first layer. Layer k (ms -1 ) s 1?? Observed Mulino delle Vene springs discharge (01/06/ /08/2013) Two steps approach: 1. Steady state simulation 2. Transient simulation k s day

11 Test 1 k = 10-4 ms -1 Δh = 357 m 1. Steady state simulation P = Q (1 st June 2013) Hydrogeological analysis k mean = 4,05x10-5 ms -1 Test 2 k = 5x10-5 ms -1 Δh = 603 m Test 3 k = 10-5 ms -1 Δh = 2962 m (Δh: difference between hydraulic head in the farthest point from the springs and the springs themselves) Water surface, Test 1. Elevation of the topographic surface. Hydraulic head Prova 1 (m a.s.l.) Elevation (m a.s.l.)

= 5x10-5 ms -1 Δh = 603 m Test 3 k = 10-5 ms -1 Δh = 2962 m (Δh: difference between hydraulic head in the

12 Simulated discharge (m 3 d -1 ) GIT Geology and Information Technology 2. Transient simulation Initial hydraulic head is set as the one obtained in the steady state simulation, then the run is started for the calibration period (from June to August) estimating the storativity that allowed the best simulation of the depletion curve to be obtained. Test 1 k = 10-4 ms -1 Δh = 357 m s = 1x10-3 R 2 = 0, Test 2 k = 5x10-5 ms -1 Δh = 603 m s = 3x10-4 R 2 = 0,9828 Test 3 k = 10-5 ms -1 Δh = 2962 m s = 1x10-6 R 2 = 0, Test 1 Test 2 Test 3 Real discharge Discharge (m 3 d -1 )

August) estimating the storativity that allowed the best simulation of the depletion curve to be obtained.

13 Validation Rainfall and snowmelt have been applied and then simulated discharge values were compared to the daily springs outflow for the whole monitoring period. R 2 01/04/ /05/ /08/ /10/2013 Test 1 0,7811 0,2474 Test 2 0,7498 0,2685 Test 3 0,7876 0,2177 Q (m 3 d -1 ) April-May Calibration Sept.-Oct R (mmd -1 ) R Real discharge Test 1 Test 2 0 time 0 Test 3

R 2 01/04/2013 31/05/2013 30/08/2013 31/10/2013 Test 1 0,7811 0,2474 Test 2 0,7498 0,2685 Test 3 0,7876 0,2177 Q

$Conclusions: 1. Hydrogeological model of the fractured aquifer was successfully implemented. 2. The large amount of available data allow analysis aimed at water resources management. 3.$ way to simulate discharge in the whole hydrogeological year.

way to simulate discharge in the whole hydrogeological year.

14 Conclusions: 1. Hydrogeological model of the fractured aquifer was successfully implemented. 2. The large amount of available data allow analysis aimed at water resources management. 3. The results have highlighted the general capability of the EPM approach for simulating springs discharging from fractured aquifers in the depletion period, however, the approach is not an efficient way to simulate discharge in the whole hydrogeological year. Outlook: Since a calibrated model can support water resources management, further efforts will be spent to take into account the different hydrogeological characteristics of the aquifer which feed Mulino delle Vene springs, particularly of the upper part which is crossed by the moreopened and less-spaced fractures, even considering more sophisticated approaches such as Multi-Domain EPM, Discrete Fracture Network (DFN) and Hybrid (EPM for matrix and DFN for fractures). Hydrogeology Springs discharge Hydrology Calibrated model

15 REFERENCES: Angelini P., Dragoni W. (1997). The problem of modeling limestone springs: the case of Bagnara (North Apennines, Italy). Ground Water, 35(4), Cherubini C. (2008). A modeling approach for the study of contamination in a fractured aquifer. Geotech Geol. Eng., 26, Diersch H.J.G. (2006) Feflow User s Manual version 5.3, Institute for Water Resources Planning and System Research Ltd., Wasy, Berlin. Francani V., Cherubini C. (2006). Approcci modellistici e confronto per lo studio del flusso e del trasporto nei mezzi fratturati. Atti del convegno GEOFLUID (Gestione delle acque sotterranee e geologia applicata all ambiente), Piacenza, 4 Ottobre 2006, DIIAR, Politecnico di Milano, Nocchi M., Salleolini M. (2012). Modellazione di un acquifero a permeabilità fissurale: il complesso vulcanico del M. Amiata (Toscana meridionale). EngHydroEnv Geology, 15, Scesi L., Gattinoni P. (2007). La circolazione idrica negli ammassi rocciosi. Casa Editrice Ambrosiana, Milano, 156. Modelling a fractured aquifer: what can be learned by the Mulino delle Vene springs (northern Apennines)? F. Petronici 1, L. Borgatti 1, D. Errigo 2, F. Cervi 1. 1 DICAM - Dipartimento di Ingegneria Civile, Chimica, Ambientale e dei Materiali - Università di Bologna. 2 ARPA Emilia-Romagna.

3, Institute for Water Resources Planning and System Research Ltd., Wasy, Berlin. Francani V., Cherubini C. (2006).

Documenti analoghi

GIT Geology and Information Technology

GIT Geology and Information Technology Application of remote sensing data and GIS techniques to the study of the morpho-structural features of extensional basins: an example from the Montefalco area (northern Apennines, Italy). Michele Santangelo