Planning Wetland Restoration in Agricultural Watersheds to improve water quality

Transcription

1 Planning Wetland Restoration in Agricultural Watersheds to improve water quality Francisco A. Comín 1, Ricardo Sorando 1, Alfonso Calvo 2, Victor Guirado 3, Nadia Darwiche 1 1 Instituto Pirenaico Ecologia-CSIC, Zaragoza, Spain 2 Confederación Hidrográfica del Ebro-MMARM, Zaragoza, Spain 3 KV Consultores, Madrid, Spain Outline Introduction Study area: River Flumen watershed Objective: A Protocol to identify and select zones to create/restore wetlands in irrigated agricultural watesheds Methods: The tools to select and prioritize action zones Results: Selected sites Discussion: Restoration Actions Creation and restoration of aquatic ecosystems to improve water quality and biodiversity

2 Introduction In intensively irrigated agricultural watersheds: -excess of pollutants discharged into rivers causes water quality degradation -wetlands can be efficient systems to retain and remove pollutants from agricultural wastewater, thus contributing to the improvement of the river water and ecosystem. -Planning wetland creation/restoration at watershed scale is required for this purpose: Objetive Establishing a protocol for restoring/creating wetlands at watershed scale to improve water quality and biodiversity.

3 Altitude (m) Study area Ebro Basin (NE Spain) River Flumen wateshed Flumen River Basin Profile Flumen 6 Isuela Distance Downstream (m) Basin area: 1431 km 2 River length: 12 km Climate: semiarid- Rainfall: 15-4 mm/yr PET = mm/yr Inhabitants: 65, Flumen av. flow: 6 m 3 /s (21) Intensively regulated Irrigation network: To the river: Irrigated agricultural lands: Drainage network: Wetlands

4 Average monthly flow (m³/s) River Flumen its watershed and its key environmental variables Water flow at the river mouth (*) 2 Relative watershed 1 land covers s o n d e f m a m j j a s o n d e f m a m j j a ARROZ 7% PASTOS 13% GIRASOL 3% BOSQUE 8% AGUA 1% URBANO 1% OTRAS 2% MAÍZ CEBADA 33% 7% TRIGO 7% FORRAJERAS 5% ALFALFA 13% Multifactorial analysis of water quality variables Key variables NO 3 vs. SS & NH 4 * Natural river drainage network Locationof sampling sites Land cover Suspended solids NO 3 concentrations along the river axis Clustering river zones by water quality similarity Target zone to restore/ create wetlands

5 Protocol steps: 1. Identifying potential sites for wetland restoration and creation 2. Site selection: adecuacy to accomplish project objectives 3. Dimensioning wetland sites 4. Accomplishing social and economic constraints Yes sg 5. Designing wetland restoration actions No

6 Criteria Protocol steps Tools -Recovering destroyed and degraded wetlands -Agreement with hidrogeomorphic characteristics of wetland sites 1. Identifying potential sites for wetland restoration and creation Land cover Maps SWAT GIS -Absolute and relative importance for removing nitrate discharge to the river -Dimensioning parameters to remove nitrate -Social constraints: Land availability for wetland creation/restoration -Economic constraints: Budget availability for wetland creation/restoration -Design characteristics for the improvement of wetland functions 2. Site selection: adecuacy to accomplish project objectives 3. Dimensioning wetland sites 4. Accomplishing social and economic constraints s 5. Designing wetland restoration actions SWAT-GIS Frequential distribution of nitrate and water discharges in sub-basins Dimensioning 1st order areal removal model for surface flow wetlands (Kadlec & Knight 1996) Checking land registry and constructing costs against available funding Constructing actions to Improve functional performance

7 1. Identifying potential sites for wetland restoration and creation: The SWAT tool Climate Delineate subwatersheds of Flumen River with direct surface run-off to the river Slope DEM model Wateshed & hydrologic network delineation Farming land uses (-fertilizer use-) Crop Soils Land cover & uses Irrigation (m3/ha per year) HRUs DELINEATION -248 HRUs- Basic dressing Fertilization (Kg NO 3 /Ha per year) SWAT-The Soil and Water Assessment Tool 29 SWAT is a river basin scale model developed to quantify the impact of land management practices in large, complex watersheds. Top dressing ALFALFA (Urea) 5 (Urea) Upstream reservoir zones are not considered Sub-basins delineation -163 subbasins- Area [ha] Area[acres] Watershed Number of Subbasins: 163 Area [ha] Area[acres] %Wat.Area LANDUSE: Spring Canola-Polish --> CANP Corn --> CORN Winter Wheat --> WWHT Italian (Annual) Ryegrass --> RYEG Alfalfa --> ALFA Winter Barley --> WBAR Sunflower --> SUNF Rice --> RICE Grain Sorghum --> GRSG Pasture --> PAST Soybean --> SOYB Forest-Mixed --> FRST Water --> WATR Residential --> URBN SOILS: FINE TEXTURE MEDIUM TEXTURE MEDIUM-FINE TEXTURE CORN (NPK ) 7 (Urea) RICE (Urea) BARLEY* (NPK ) 2 (Urea) SLOPE: WHEAT (NPK ) 25 (Urea) Every delineated subbasin (163) has a potential site for wetland creation/restoration at the subasin outlet

8 Dec-9 Jan-1 Feb-1 Mar-1 Apr-1 May-1 Jun-1 Jul-1 Aug-1 Sep-1 Oct-1 Nov-1 Dec-1 NO3 (mg/l) Jan-4 May-4 Sep-4 Jan-5 May-5 Sep-5 Jan-6 May-6 Sep-6 Jan-7 May-7 Sep-7 Jan-8 May-8 Sep-8 Jan-9 May-9 Sep-9 Jan-1 May-1 Sep-1 Flow (m3/s) Precipitation (mm) 2. Site selection: Selecting subbasins with high nitrate discharge Calibrating the SWAT model for water and NO 3 discharge at the watershed outlet 3 OUTLET FLOW RIVER FLUMEN BASIN OBSERVED SIMULATED PRECIPITATION HUESCA PRECIPITATION SARIÑENA OUTLET NO3 CONCENTRATION FLUMEN RIVER BASIN OBSERVED SIMULATED

9 2. Site selection: Selecting subbasins with high nitrate discharge The calibrated model is applied to all delineated subasins of the target area for obtaining water, suspended solids and nitrate discharges SWAT provides quantity and quality flow data, sediment transport and pollution accumulation in river channel and soils for all the river sections of each subbasin. Depending on the time scale of the input information we can obtain daily, monthly or yearly results (monthly in this case). Subbasin Area Flow coming out of the subbasin Sediment coming out of the subbasin Nitrate coming out the subbasin (annual discharge) SU YEA MO AREAk FLOW_IN Q m 3 FLOW_OUT SED_INt SED_OUTt ORGN_I ORGN_OU ORGP_I ORGP_OU NO3_INNO3_OU /d B R N m2 cms cms ons ons Nkg Tkg Nkg Tkg kg Tkg , , , , , , , , E E , E E , , , , , , , E , E E , E E

10 January-4 May-4 September-4 January-5 May-5 September-5 January-6 May-6 September-6 January-7 May-7 September-7 January-8 May-8 September-8 January-9 May-9 September-9 January-1 May-1 September-1 FLOW (l/s) and NO3 CONCENTRATION (mg/l) Precipitatation (mm) NO3 (mg/l) Janua May-4 Septe Janua May-5 Septe Janua May-6 Septe Janua May-7 Septe Janua May-8 Septe Janua May-9 Septe Janua May-1 Septe FLOW (l/s) and NO3 CONCENTRATION (mg/l) Precipitation (mm) NO3 (mg/l) 2. Site selection: Selecting subbasins with high nitrate discharge Two selected subbasins SWAT simulation of water and and nitrate discharges for every subbasin 3 25 (9.84 Km2). SUBBASIN Nitrate (mg/l) vs Flow (l/s). Subbasin 117 Subasin 76 2 CAUDAL MEDIO (l/s) CONCENTRACIÓN MEDIA NO3 (mg/l) 1 15 PRECIPITACIÓN SARIÑENA Flow (l/s) Subasin (35.34 Km2). SUBBASIN Nitrate (mg/l) vs Flow (l/s). Subbasin CAUDAL MEDIO (l/s) CONCENTRACIÓN MEDIA NO3 (mg/l) PRECIPITACIÓN SARIÑENA Flow (l/s)

11 Area (Ha) Flow (ldm3/yr) and Nitrate (Hg/yr) Area (Km2) Flow (l/s) and Nitrate (mg/l)) 2. Site selection: Selecting subbasins with high nitrate discharge Natural wood & grassland areas and upstream reservoirs zones are not considered 3 25 AVERAGE VALUES AREA (Km2) Flow (l/s) Point source polluting areas -cities and pig farms are not considered here Subbasin ABSOLUTE VALUES Area (Ha) Flow (Dm3/year) Nitrate (Hg/year) Non irrigated dry cereal areas are not considered Subbasin 7 subbasins with high non-point agricultural NO 3 discharge are selected

12 NO3 (mg/l) 3. Dimensioning wetland sites The first order areal model to estimate the wetland area to achieve Subbasin 117 SWAT modelled NO 3 concentrations vs. water discharges Flow (l/s) a target outlet nitrate concentration (Kadlec & Knight 1996) FLOW_IFLOW_ SED_INt SED_OUORGN_I ORGN_ SUB SUB YEAR MO Q m3/d AREAkm2 Ncms OUTcms ons Ttons Nkg OUTkg A= (,365 Q/k) ln(c i -C*/C o -C*) where A-wetland area (ha) C i -inlet concentration (mg/l) (minº concentration of the third quartile=maxº 75th percentile) C o -outlet concentration (mg/l) (target outlet concentration 2 mg/l) Q- water flow rate (m 3 /d) (third quartile of the range of N=3 concentrations selected) K-first order areal rate constant (35 m/yr) A-wetland area (ha) ORGP_I ORGP_ Nkg OUTkg NO3_IN kg NO3_OUN3_ in Tkg mg/l Wetland Area (ha) , , , , , ,175 19, , ,2997 2, , ,748 12, , ,24 52, , ,929 21, , ,165 54, ,31E-4 2,31E , , , , , , E ,85E , , , ,8931 2, , , , , , , , ,858 9, , ,967 34, , ,731 13, ,15 97, , E , , , ,38E-4 1,38E , , , E-7 1,53E ,755 92,9797

13 4. Accomplishing social and economic constraints s Select the next subbasin/ wetland -Set the subbasins in order of decreasing estimated wetland area and proceed one after the other following this order Select the next subbasin/wetland -Social constraints: There is a (public-free) land area available at the subbasin No Yes -Economic constraints: There is funding available for a simple extensive surface flow wetland creation/restoration No 2 wetland sites of 7 selected of 163 potential subbasins Other constraints Yes 2 wetlands (subbasins-sites) are affordable to be restored/created with this project 5. (Detailed) Design restored/created wetlands

14 Area (ha) 2 wetland sites selected and affordable with this project Area (ha) NO 3 (mg/l) Water flow (m 3 /d)

15 Before (211) Before (211) Sub-basin 76 (35 km 2 ) Wetland: m 3 /d; 17 mg/l; 54 ha After (212)

16 Before (211) Before (211( Sub-basin 117 (9,87 km 2 ) Wetland:2779 m 3 /d; 2 mg/l; 13,5 ha After (212)