|OUYANG, YING - Us Forest Service (FS)|
|LEININGER, THEODOR - Us Forest Service (FS)|
Submitted to: Water Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2016
Publication Date: 5/24/2017
Citation: Ouyang, Y., Feng, G.G., Read, J.J., Leininger, T., Jenkins, J.N. 2017. Estimating the ratio of pond size to irrigated soybeans land in Mississippi: A case study. Water Science and Technology. pp. 1639-1647.
Interpretive Summary: In this study, a STELLA model developed previously (Ouyang et al., 2015) was applied to investigate the annual pattern of pond hydrological processes, determine the ratio of pond size to irrigated crop land, and estimate the mitigation of groundwater depletion due to the use of an on-farm storage pond. A typical annual pond evaporation pattern, with increasing from winter to summer followed by decreasing from summer to next winter, was observed for a 10-year simulation period. The annual pond evaporation was controlled by air temperature and solar radiation and the pond water level was relative stable for conditions without using pond water for irrigation. In contrast, dramatic changes in pond spill and water level were observed for conditions with using pond water for irrigation. A reasonable ratio of pond size to the soybeans irrigation land area was estimated to be 1:18 if the irrigation rate was 2.54 cm/d (or 1in/d) and the average pond water level was above 0.38 m (or 15in). A maximum ratio of pond size to irrigated soybeans land could be 1:20 for the entire 10-year period if pond water level was kept near zero. We postulated that if a 10,000-ha soybean land was irrigated with pond water under the ratio of 1:18, it could reduce the loss of groundwater by 11%. This study showed that on-farm storage pond is one of the promising alternatives to conserve groundwater resources. Further study is warranted to estimating the optimal contributing drainage watershed area for runoff water collected by pond.
Technical Abstract: Although more on-farm storage ponds have been constructed in recent years to mitigate groundwater resources depletion in Mississippi, little effort has been devoted to estimating the ratio of pond size to irrigated crop land based on pond matric and its hydrological conditions. Knowledge of this ratio is crucial to determine pond size for construction and to manage pond water for irrigation. In this study, two simulation scenarios were chosen to determine such a ratio as well as to investigate pond hydrological processes using a STELLA (Structural Thinking, Experiential Learning Laboratory with Animation) model, one scenario with and the other without using pond water for irrigation for a typical pond that represented the average conditions in East Mississippi. Simulation results showed that the average rate of pond evaporation ranged from 20 cm3/d/pond in winter to 50 cm3/d/pond in summer for a 10-year simulation period from 2002 to 2011. Pond water level changed slightly for conditions without using its water for irrigation. In contrast, the pond water level changed dramatically for conditions with using its water for irrigation. A reasonable ratio of pond size to irrigated soybeans land was 1:18 if the irrigation rate was 2.54 cm/d (or 1 in/d) and the low limit of the pond water level was above 0.38 m (or 15 in), while a maximum ratio of pond size to irrigated soybeans land was 1:20 if the pond water was drawn to near zero. Under the ratio of 1:18, a 1-ha pond with an average depth of 2m could irrigate 18-ha soybeans land. For the ratio of 1:18, our simulations further revealed that a 1-ha soybeans land could save about 542 m3 groundwater each year. If the average loss of groundwater is 493,000,000m3/y in some part of Mississippi due to irrigation, a 10,000-ha soybean land irrigated with pond water could save groundwater resources by 11% (5,420,000/493,0000,000 = 11%) each year. Results suggest that on-farm storage pond seems to be one of the promising alternatives to conserve groundwater resources.