Climate change Adriatic coast Emilia- Romagna (Italy): wet and dry seasons more distinct.

Transcription

1 DISCONTINUOUS RECHARGE OF FRESH WATER LENSES ALONG THE ADRIATIC COAST, ITALY Pauline Mollema and Marco Antonellini, University of Bologna (Italy) Gualbert Oude Essink, Deltares (Netherlands) Climate change Adriatic coast Emilia- Romagna (Italy): wet and dry seasons more distinct Average Monthly precipitation [mm] Dec Jan Feb Mar Apr May June July Aug Sep Oct Nov Temperatura Max [ C] Prec. [mm] Tmax ( C) Annual Prec = 626 mm Tmax average = 19 C Mollema- Modelli numerici 1

2 Study area, Ravenna, Italy: Apennine river basins. Po Regione Emilia-Romagna Po river shed Fresh water imported from Po river and Apennines Regione Emilia-Romagna Po River Bologna Ridracoli Ravenna Marina Romea Apennine Mollema- Modelli numerici 2

3 Subsidence, polders, old and new dunes Holocene West Paleo dune Polders Dune & beach deposits Salt water marsh Coastal Dunes (Marina Romea) m msl Pleistocene 15 km -3 m msl Study Area Marina Romea, Province of Ravenna, Italy Google Mollema- Modelli numerici 3

4 Lamone River Salt water marshes Pialasse A A Town of Marina Romea Coastal dunes Bathing establishments Between relics of dunes Adriatic sea Pine Forest 1 km Canale Candiano Water table [m M.S.L.] Watertable in Piezometers PZMR1B, PZMR2B, PZMR3B and PZMR 4B A A.4 West East Sea.3 Pine forest.2.1 Pialasse PZMR1B PZMR2B -.3 PZMR3B PZMR4B -.4 Distance from Pialasse measured along profile [m] Mar 7 Apr 7 May 7 Jun 7 Jul 7 Aug 7 Sep 7 Oct 7 Nov 7 Dec 7 Jan 8 Feb 8 Mollema- Modelli numerici 4

5 Salinity [g/l] Salinity at bottom piezometres West East Pialasse Adriatic Sea Pine forest PZMR1B PZMR3B PZMR4B PZMR2B Distance from Pialasse Mar 7 Apr 7 May 7 Jun 7 Jul 7 Aug 7 Sep 7 Oct 7 Nov 7 Dec 7 Jan 8 Feb 8 Fresh water lens surrounded by salty sea Ground water recharge B Freshwater lens ρ f h H Sea Hmax ρ s Saline Groundwater 1 m 9/12/29 P. Mollema 1 Mollema- Modelli numerici 5

6 2D SEAWAT MODEL (MODFLOW + MT3DMS + DOUBLE DENSITY) 6 m Constant head = Constant concentration = 3 g/l Recharge boundary from 3-4 m No Flow No flow Sand K = 6.9E-4 m/s Clayey loam 5.8E-6m/s Clay 3.5E-9m/s Clayey loam 5.8E-6m/s Sand K = 6.9E-4 m/s How much (natural) recharge? Evaporation from leaves Precipitation Evaporation from soil Ground water inflow Transpiration Soil moisture Capillary Recharge rise infiltration Irrigation= Run off = mm Drainage= a lot Ground water outflow Modified from FAO 1998 Mollema- Modelli numerici 6

7 Recharge = Precipitation-Potential Evapotranspiration Prec. [mm] PET [mm] Surplus-Deficit Recharge. -1. Dec- Jan_Feb March-Apr- May June-July- Aug Sep-Okt- Nov No recharge Daily recharge [mm] in models, applied in 4 stress periods per year. Daily Recharge [mm] Dec- Jan- Feb March-April- May-June-July- August Sep- Oct- Nov Day of the year starting at 1 December Discontinuous Continuous Total annual recharge: 136 mm (current) 68 mm (future?) 34 mm (future?) 272 mm Mollema- Modelli numerici 7

8 5/2/8 Development of fresh water lens T= 9 days T= 18 days T= 5 days T= 5 days (136 yrs) P. Mollema 9/12/29 15 Definition thickness fresh/brackish water water: depth to 2g/l contoura 2g/l Salicornia Europaea Pinus Pinea Antonellini and Mollema, 21 Mollema- Modelli numerici 8

9 Total annual recharge 136 mm Sand Sandy Silty Loam Sand continuous discontinuous Total annual recharge 68 mm continuous discontinuous Mollema- Modelli numerici 9

10 Fresh/brackish water depth vs annual recharge Depth to 2g/l contour [m] 14 Depth to 2g/l contour [m] Depth to 2g/l contour [m] Critical recharge Total 1 annual recharge 2 [mm/year] 3 Total annual recharge [mm/year] Total annual recharge [mm/year] Discontinuous recharge Discontinuous (sand 9.5 recharge m) (sand 9.5 m) Continuous recharge (sand 9.5 m) Continuous recharge (sand 9.5 m) 9/12/29 P. Mollema 19 Critical recharge sand layer of 7.5 m thick. 14 Depth to 2g/l contour [m] Critical Recharge Annual Recharge [mm/yr] Continuous recharge (sand 7.5 m) Discontinuous recharge (sand 7.5 m) Mollema- Modelli numerici 1

11 Concluding remarks In areas with little and discontinuous recharge, fresh water lens may exist because of alternating periods of recharge and no recharge. Thickness of aquifer influences value of critical recharge. Implications for Managed Aquifer Recharge Implications for Management of coastal Mediterranean aquifers 9/12/29 P. Mollema Thank you for your attention. 9/12/29 P. Mollema Mollema- Modelli numerici 11