**Other Abstract** | According to the monitoring and experiments in flood seasons during 2011-2012
in the Hougou agricultural watershed, we carried out the transport mechanisms and
modelling studies of water and sediment erosion and non-point source pollution，
discussing the interception of soil and water conservation measures and reduce
effectively of agricultural non-point source pollution for the South-North Water
Diversion Project. By the method of combining theoretical analysis and experiments
study, the main results were as follows:
(1) Clarify the characteristic of runoff and spatial and temporal distribution of
sediment yield. During the flood season, there is in highly significant correlation with
rainfall and runoff in runoff plot, among there was a highly significant linear correlation
in the 9° plot，there existed very significant curve function correlation in 14°-25° plots.
Moreover, the rainfall of critical runoff yield decline with slope degree increase.
Stored-full runoff was the main pattern of runoff yield in slope farmland in the
Hougou agricultural watershed, and the subsurface flow accounted for a larger
percentage of total runoff. Moreover, the subsurface flow ratio is 1.14-1.35 times at the
seedling stage and the vigorous stage.
Runoff rate is increase with volume of runoff increase; there is power function and
linear relation between runoff velocity and runoff volume in the early and the later of
flood season. There are power functions and linear relation between runoff kinetic
energy and sediment loss in the early and the later of flood season, however, power
function relation in the middle of flood season.
(2) The SCS model not only reflects the runoff yield conditions under different
soil types and vegetation covers in the Hougou agricultural watershed, but also fully
considered the soil moisture impacts runoff. When loss parameter is 0.3, and CN value is 58, monitored runoff and calculated runoff is very closer in runoff plot in the Hougou
agricultural watershed.
(3) Clarify the change laws of soil erodibility under different land use and
elevations. The study of slope indicated that soil erodibility of woodland，abandoned
land and cornfield is drop off over increasing elevation, the maximum soil erodibility at
the point of 309 m, then declines gradually，the minimum soil erodibility of terraced
field at elevation between 420 m and 430 m, the value is tending towards stability.
(4) Clarify the effect of the rainfall erosivity and soil erosion modulus under
different land use, and reveal the relation between runoff and sediment yield. The
maximum rainfall erosivity in July, average R value is 3403.66 MJ·mm/ （hm 2 ·h·a）, and
average soil erosion amount is 15587.41t/a, soil erosion modulus is 2013.877 t/(km 2 ·a) ,
which in the scope of middle soil erosion intensity in the Hougou agricultural
watershed. However, average soil erosion amount of slope land is 9853.47 t/a, which
takes up of more than 63.2% in total soil erosion amount.
The order of soil erosion amount in different land use is: garden field＞slope land
＞abandoned land＞orchard field.The results showed that the maximum soil erosion
amount of slope land, abandoned land, garden field, orchard field in July, which takes
up of more than 31.76%, 32.78%, 39.05%, 11.44% in total soil erosion amount in a rain
event during flood season, respectively.
The best regression equation is cubic curve-fitting equation between soil loss
amounts and runoff of orchard field, however, the best regression equation is S curve
equation between soil loss amounts and runoff of slope land, abandoned land, garden
field.
(5) The N and P loss processes shows in stages obviously in flood sesons during
2011-2012. N and P loss predictions done stage-by-stage can have improved accuracy.
Although the fitted equations between the amount of N and P loss between runoff and
sediment yield were N=aR b S c assessed stage-by-stage, the method was supported by the
study for predicting the amount of N and P loss in the Hougou agricultural watershed.
The process of N and P loss in runoff and sediment is different obviously under
different land use. The N and P loss concentrations in orchard field and garden field
have exceeded surface water Class Ⅱ water standard more than 15 and 1.25 times. For four land uses, the order of N and P loss is garden field＞abandoned land＞slope land
＞orchard field. According to the monitored results, average TN amount loss of garden
field, abandoned land, slope land, orchard field are 15.29, 7.20, 4.92, 1.37kg/(hm 2 ·a),
however, average TP amount loss of garden field, abandoned land, slope land, orchard
field are 0.25, 0.22, 0.09, 0.05kg/(hm 2 ·a), respectively.
(6) Reveal the relation between runoff, sediment and TN, TP concentration. The
cubic function can express relation between the TN concentration in runoff and runoff
from slopeland, abandoned land, garden field, orchard fields, especially orchard field.
The cubic function can express relation between the TP concentration and sediment
from slopeland, abandoned land, garden field; however, S curve equation; power
function and logistic equation can express the relation in orchard fields.
(7) Ditch water of different sections was monitored at different times to study the
ecological effectiveness of ditch. The results showed that ditch and aquatic plant had
function of interception and purification water. N and P concentration of water
decreased when water flow through the ditch. Generally reduction range of TN and was
higher than that of TP. Moreover, reduction range of NH 4 + -N was higher than that of
TN. However, NO - 3 -N concentration had slight fluctuated incremental trend in ditch
after rains. The coefficient of variation of TN, NH 4 + -N, NO - 3 -N and TP in different
sections is downstream＞upstream＞midstream. The coefficient of variation of TP is
the highest; the range is 48.32-113.66%, and the coefficient of variation of NO - 3 -N is
the smallest; the range is 9.71-20.24%.
Key Words ：Agricultural non-point source pollution, Sediment yield processes, N and
P loss processes, Controlling, the middle reaches of Han River |

## Edit Comment