Mole drain performance in a clay loam soil in Ireland

Figures & data

Figure 1. (a) Location and surface topography map of study area, 1 (b) field and plot boundaries and piezometer locations (1) upslope, (2) mid-slope and (3) downslope.

Table 1. Soil profile texture and estimated hydraulic conductivity.

		<2 mm
Depth	>2 mm (%)	Sand (%)	Silt (%)	Clay (%)	USDA textural class	ks^a (m day^−1)
0–25	11.5	41.3	23.4	35.3	Clay loam	0.047
25–80^b	25.5	30.9	23.8	45.3	Clay	0.015
80–130	28.3	34.2	21.7	44.1	Clay	0.014
130–200	1.0	5.9	25.8	68.3	Clay	0.007

Note: USDA, United States Department of Agriculture.^aEstimated using the hydraulic properties calculator of Saxton and Rawls (2006).

^b Depth range over which the mole drains and gravel mole drains were installed.

Table 2. Pre-event and event precipitation characteristics of the 12 selected events.

	Event duration	7-day antecedent precipitation	30-day antecedent precipitation	Antecedent SMD	Rainfall	Maximum intensity	Mean intensity	ED
Event	(h)	(mm)	(mm)	(mm)	(mm)	(mm/h)	(mm/h)	(mm)
1 (02/06/12 to 03/06/12)	23.75	6.0	34.0	30.0	63.8	8.0	2.69	21.3
2 (06/06/12 to 08/06/12)	45.25	72.0	92.0	−8.1	37.4	11.2	0.83	30.4
3 (18/06/12 to 19/06/12)	18.25	31.4	142.8	−6.8	12.0	6.4	0.66	7.2
4 (20/06/12 to 22/06/12)	52.75	38.4	154.8	−6.9	22.4	5.6	0.42	14.5
5 (12/08/12 to 13/08/12)	39.50	6.8	78.4	0.9	38.6	20.0	0.98	23.1
6 (14/08/12 to 17/08/12)	68.00	42.4	112.0	−10.0	39.6	10.4	0.58	31.5
7 (16/10/12 to 17/10/12)	39.25	37.8	95.8	−9.6	30.4	3.2	0.77	27.9
8 (17/11/12 to 20/11/12)	71.00	17.6	66.6	−9.9	24.6	1.6	0.35	22.2
9 (19/12/12)	7.50	35.0	107.0	−9.3	10.4	4.8	1.39	9.2
10 (27/12/12)	46.00	41.2	115.0	−10.0	11.8	3.2	0.26	10.4
11 (17/01/13 to 19/01/13)	41.50	10.8	95.6	−10.0	40.8	7.2	0.98	39.8
12 (09/02/13 to 11/02/13)	33.50	19.0	119.8	−8.8	13.4	3.2	0.40	10.6

Figure 2. (a) Daily precipitation, (b) ED and (c) SMD (Schulte et al., 2005) for the period 01/04/12 to 01/04/13 during which the rainfall events were selected. Arrows in (a) indicate the start of the events.

Table 3. Soil moisture status on treatment installation dates.

				Gravimetric moisture content (g g^−1)
Treatment: date	7-day antecedent precipitation (mm)	30-day antecedent precipitation (mm)	SMD (mm)	0.0–0.3 m	0.3–0.6 m
B: 31 January 2011	3.1	52.3	−2.3	0.49	0.35
D: 12 July 2011	38.1	105.3	2.8	0.39	0.21
C: 14 July 2011	14.6	102.9	9.7	0.39	0.21

Figure 3. Relationship between mean OF and ED (R² = 0.79, P < .001) and mean DF and ED (R² = 0.39, P < .001).

Figure 4. Mean total OF and DF during 12 events from treatments; A (undrained control), B (mole drains installed in January 2011), C (mole drains installed in July 2011) and D (gravel mole drains installed in July 2011). Error bars show the treatment standard error of mean. Mean ED was 20.7 mm. Any water not accounted for as OF or DF is assumed to contribute to groundwater recharge.

Figure 5. Total OF and DF per event for treatments. (a) A (undrained control), (b) B (mole drains installed in January 2011), (c) C (mole drains installed in July 2011 and (d) D (gravel mole drains installed in July 2011). Error bars show SD.

Figure 6. Ratio of total OF and DF to ED per event for treatments (a) A (undrained control), (b) B (mole drains installed in January 2011), (c) C (mole drains installed in July 2011 and (d) D (gravel mole drains installed in July 2011). Error bars show standard deviation.

Saxton KE, Rawls WJ. 2006. Soil water characteristic estimates by texture and organic matter for hydrologic solutions. Soil Sci Soc Am J. 70:1569–1578. 10.2136/sssaj2005.0117

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Schulte RPO, Diamond J, Finkele K, Holden NM, Brereton AJ. 2005. Predicting the soil moisture conditions of Irish grasslands. Irish J Agr Food Res. 44:95–110.

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