Landscape Water Management Strategies To Optimise Stormwater at RBG Melbour ne

Transcription

1 Landscape Water Management Strategies To Optimise Stormwater at RBG Melbour ne Geoff Connellan, G&M Connellan Consultants ( & Peter Symes, Royal Botanic Gardens (RBG) Melbourne ( Stormwater Vic 2013 Conference, Melbourne

2 High Value Landscape Delivers Social, Environmental and Economic Benefits

3 Stormwater supply Critical Issues Importance of a balanced approach: Maximising use of stormwater Protection of the storage including aquatic vegetation Keeping landscape plants healthy through maintenance of soil moisture Keeping the soil environment healthy

4 a. Landscape water demand Topics b. Rainfall contribution - Throughfall trials - Soil infiltration - Mulch absorption, Hydrophobic soils c. Irrigation application effectiveness d. Irrigation management -Refill point -Soil water holding capacity (Organic content) - Stress indicators (ETSI) e. Soil water banking f. Storage water quality indicators

5 RBG Melbourne Site Aerial

6 Schematic of RBG Stormwater Project Yarra River **On average, about 70 ML expected to be delivered per annum Lake Urban catchment Volcano Urban catchment

7 Eucalypt Species Rainfall Requirements Annual Average of 544 mm

8 Selected Australian native species (83) growing at RBG Melb. Annual Average of 544 mm

9 a. Landscape Water Demand Major influencing factors: Plant species Plant performance standards Climate Site microclimate and planting density Soil conditions Soil moisture available

10 Estimating Plant Water Demand ET L = K L x ETo ET L K L ETo Evapotranspiration rate of plants Landscape coefficient Reference evapotranspiration

11 Water budgets - Estimating Water Demand Water use is dependent on plant condition What plant condition is required? Tree Condition

12 Determination of K L Ks 0.5 Viburnum Bed (5A) Kmc - Microclimate 1.0 Kd Density 1.3 K L = Ks x Kmc x Kd

13 Typical Landscape Coefficients (KL) used in summer at RBG Melbourne K L 0.4 K L <K L 0.3 K L 0.5

14 Landscape Site Water Cycle Tree water balance

15 b. Rainfall contribution to soil moisture Measuring Effective Rainfall and Irrigation Throughfall measurement apparatus Catch cans Note: Event-based interception loss can be up to 80-90% Up to 60% of rainfall can be intercepted per month Source: Dunkerley D (2011) Geo.Research Abstracts Vo 13, EGU

16 Effective Rainfall Measurement Measurements are yearly averages and do not include rainfall amounts less than 2 mm (Actual annual rainfall reaching the surface is less) Additional moisture loss is expected in mulch/leaf litter layers

17 c. Irrigation Application Efficiency APPLICATION EFFICIENCY OVERALL IRRIGATION EFFICIENCY SCHEDULING EFFICIENCY *Both need to be high to achieve High Overall Irrigation Efficiency

18 Hydrophobic Soils * Loss of efficiency Risk conditions Extended dry periods Typically sandytextured soils High organic contents

19 d. Irrigation Management Soil water storage Soil Water Holding Capacity Refill point Stress set point (ETSI) Soil moisture sensing

20 Soil Water Properties

21 RBG Melb. Soil Water Properties Soil Type Soil Water Holding Capacity (%) Precent Increase Compared to General Loam (%) General loam 24 0% Fine sandy loam % High organic, sandy loam High organic content, well structured loamy soil % %

22 Project: Water management of complex landscapes using soil moistur e sensor s. RBG Melb., Melb Uni. & Sentek Pty Ltd Wireless communication to a web host 5 sensors to 700 mm

23 RBG Soil Water Profiling Soil moisture readings: 10 cm, 20 cm, 30 cm, 40 cm and 50 cm 10cm 20cm 30cm 40cm 50cm

24 e. Stormwater Harvesting and Deep soil storage Water banking Large storage required

25 RBG Melbourne, Herbarium Bed Mixed trees and shrubs SMS used to show trends in total water stored deep root system layers. Summed water in 400 mm and 500 mm soil layers. Feb Feb Feb TotalHerbarium400500RBG

26 f. Storage Water Quality Water storage and treatment Irrigation application

27 Landscape Water Quality Risks - Landscape plantings Toxins Foliage scorch Disease

28 Water Quality Irrigation Preferred Range Chemical (2) Parameter Preferred Range Comment Chloride (Sprinkler) < mg/l Foliar damage Chloride < mg/l Toxicity Sodium < mg/l Toxicity; nutrient balance, soil structure Nitrogen (Total) < 5 mg/l Irrigation nutrient balance/uptake Nitrogen (Total) < mg/l Storage health Phosphorous (Total) Phosphorous (Total) <0.5-5 mg/l Irrigation nutrient balance/uptake < 0.05 mg/l Storage health: algae

29 Water Quality Irrigation Preferred Range Chemical (3) Metals Parameter Preferred Range Comment Boron < 0.5 mg/l Plant toxicity; nutrient balance Copper < 0.2 mg/l Soil micro-organisms; nutrient balance Iron < 0.2 mg/l Aquatic health. Precipitates, nutrient balance Zinc (Soluble) < 2 mg/l Toxicity; nutrient balance; should be minimised to avoid accumulation in soil

30 Nitrogen (Total) RBG Lake Water Quality Results Parameter Preferred Range RBG Average (Since August 2012) < 5 mg/l Phosphorous (Filterable Reactive P) <0.025 Boron < 0.5 mg/l 0.11 Copper < 0.2 mg/l 0.02 Iron < 0.8 mg/l 0.58 Zinc (Soluble) < 2 mg/l 0.10

31 Landscape Water Quality Risks - Soil health Soil structure Soil health a. Physical b. Chemical c. Microbiological Soil toxins Disease Soil salinity roots Soil nutrient balance i.e. High P impacts on Fe

32 Soil Health *High organic content promotes populations of micro-organisms that both assist with nutrient cycling and limit pathogen numbers Requirements 1. Soil oxygen 2. Root exploration Root of RBG Separation Tree - mycorrhizal fungi found growing 3. Micro-organism activity 4. Water movement 5. Water storage

33 Summary/ Main Messages Efficiency of water use is extremely important Management of storage level to balance water use and aquatic plant health and function Deep soil storage to increase opportunity to use stormwater and reduce evaporation losses Monitoring of storage, inflows and soil health to achieve sustainable storages and landscape

34 Optimisation of stormwater